You would HATE being a person who could read in the Middle English era. There was no standardized spelling, people used many different conventions/regional spellings, and it was mostly either phonetic spelling or random French bullshit. Also some earlier writers used really conservative spelling to emulate Old English. It was the wild west out there.

For example, here's a (not comprensive) list of the variant spellings you may see for each second person pronoun:

Singular Nominative 2P:

thou, thoue, thow, thowe, thu, thue, þeu, þeou, thouȝ, thugh, thogh, ðhu; þou, þoue, þow, þowe, þu, þue, þouȝ, þugh, þogh, þo

(after alveolars and in contractions): tou, towe, touȝ, tu, to, te

Singular Objective 2P:

the, thee, thei, thi, thie, thy, ðe, de, þeo, þhe, yhe, ye, þe, þee, þi, þy

(after alveolars and in contractions): te

Singular Genitive, Dative, and Possessive 2P:

(usually before consonants): thi, thy, thei, they, yhi, yi, þhi; þei, þey, þy

(usually before vowels and "h"): thin, thyn, thine, thyne, thien, thyen, thein, theyn, thinne, yin; þin, þyn, þine, þyne, þinne; þines

(female referent): þinre, þire, þinen

(after "t" or "d"): ti, ty, tin, tyn, tine, tines

Plural Nominative 2P:

ye, yee, yeȝ, yhe, yie, iye, iȝe, hye, hie; ȝe, ȝee, ȝhe, ȝie, ȝeo; ge, gie, geo

Plural Objective 2P:

you, yow, youe, yowe, yo, yoe, yogh, yau, yaw, yeu, yew, yhu, yu, yw, yhow, yhou; ȝou, ȝow, ȝouȝ, ȝowȝ, ȝowe, ȝo, ȝu, ȝw, ȝuw, ȝue, ȝiou, ȝeu, ȝew, ȝewe, ȝau, ȝaw, ȝhou, ȝiu, ȝeou, ȝehw, ȝhowe; gou, gu, giu, geu, geau; ou, owe, eou, eow, eow, eo, eu, euwȝ, æu, hou, heou, heu

Plural Genitive & Dative 2P:

your, youre, yowr, yowre, ȝour, ȝoure yowyr, yowur, yor, yur, yure, yeur, yhure, yhour, yhoure; ȝowyr, ȝowur, ȝor, ȝore, ȝur, ȝure, ȝiore, ȝhour, ȝhoure, ȝaure, ȝiure, ȝiwer, ȝeur, ȝeure, ȝeuer, ȝeuwer, ȝewer, ȝewere; gur, gure, giur, giure, giuor, giuer, giuwer, giwer; ihore, ihoire, iure, eour, eoure, eouer, eouwer, eouwere, eower, eowwer, eore, eur, eure, euwer, euwere, eowrum, æure, our, oure, or, ore, ouer, ouwer, ouwere, ower, owur, hour

(early ME): þinen (genitive), þinum (dative), þirum (dative fem.)

Plural Possessive 2P:

youres, yourez, yours, youris, yurs, yowres, yowris, yowrys, yourn, youren; ȝours, ȝoures, ȝouris, ȝourys, ȝowers, ȝores, ȝures, ȝuris, ȝhurs, ȝourn, ȝouren; eowræs

You can find a lot more about Middle English spellings in LALME (A Linguistics Atlas of Late Mediæval English) (electronic version here)

Some of the more innovative spellings come from Northern Middle English/Northumbria (northern England and southern Scotland, though the dialects of the latter would largely split off and develop mostly on its own in the early stages of Middle English and become Scots) and to a lesser extent Midlands Middle English/Mercian, in large part due to significant past influence of North Germanic/Scandinavian languages; i.e., Old Norse, which was somewhat mutually intelligible with Old English and caused/progressed both the loss of inflections and the formation & solidification of Modern English syntax (in particular, Old English syntax shifted to become near-identical to Old Norse syntax; Old English also entirely lost inflection of grammatical gender, grammarical case, etc. and adopted many core vocabulary of Old Norse). Those changes happened primarily to facilitate communication with vikings in the Danelaw, since Anglo-Saxons and Scandinavians were very eager to communicate with each other; things like declensions were very different in the two languages (the 12 different declensions of "the" probably weren't fun to deal with for Scandinavians), so Old English speakers started omitting or simplifying them, and they mostly died off in (early) Middle English. English also completely lost dual pronouns (pronouns with exactly 2 referents). Word order was primarily SVO in Old Norse, so Old English's relatively liberal word order (or lack of consistent word order) was simplified/regularized significantly to be more SVO.

Southern Middle English – the dialects of West Saxon and Kent – were significantly more conservative (partly due to having next to no influence from Norse). Those are where many more conservative spellings are from. The West Saxon dialects were the most influential/dominant (especially due to the Kingdom of Wessex' great power) until the Norman Conquest, when East Midlands English (especially around London) took over that role.

Southern American English & Maritime Canadian English varieties were both primarily based on more southern English varieties – specifically, the time's London English and West Country English. Appalachian English was also heavily influenced by Scottish English and the English of northern England. Canadian English in general was based on both Southern and Midlands English. Meanwhile, New England's English was primarily derived from East Midlands dialects. Generally, dialects derived from the time's West Country English are significantly more conservative and more similar to the general speech of ~15th century England, while more Midlands (of the time) influenced American and Canadian varieties are similar to standard ~17-18th century English. Dialects influenced by the time's Scottish English and Northern English also generally contain a lot more conservative Anglic constructions – modern Appalachian/Southern American English varieties and modern Scottish/Northern varieties share a large amount of vocabulary and other features which were lost in other dialects.

Standard varieties of Modern British English are comparatively generally significantly more innovative and don't share many features with Middle & Early Modern English varieties – general British English started diverging greatly from most other English dialects around the mid-to-late 18th century and early 19th century. This is also a reason why Australia and New Zealand English have a lot of features which seem to only partially agree with other English varieties. For example, the trap-bath vowel split, which was partially completed in Australia and is present in certain words, but not all words, and has variation in some words. When Australia was being colonized, Southern English varieties had recently begun undergoing the split, and it was considered a "Cockneyism" until Received Pronunciation was formed in the late 19th century and embraced it; it wasn't fully progressed until around that time, which is why New Zealand English (which came from immigrants in the mid 19th century) mostly agrees with Southern English on those vowels.