Bit late but nobody really answered the core question yet so:

Intake fans: Intake fans are generally used in conjunction with exhaust fans to create airflow and improve cooling. This is why computers have two fans (at least) and so forth.

Exhaust fans: In addition to the above, exhaust fans are also used to control emissions/pollutants. If your printer has an exhaust fan it should, bare minimum, have a cheap carbon filter attached to it. A proper exhaust system is theoretically better but that tends to be better handled as a fume hood.

So when would you use either? A rule of thumb is that exhaust should probably always be on (while printing) if only to mitigate fumes and particulates. Even with the door open it will still help a bit. This applies to both "safe" filaments like PLA and outright toxic stuff like ABS.

As for intake? You probably also want it on any time the exhaust fan is on (so always) just to improve airflow and make the exhaust fan more effective. You aren't going to pull a vacuum without it but it still helps.

So when would you control them separately? I would probably say "never" but I could see a case where you have a particularly toxic low temperature/fragile filament (like TPU cut with a lot of ABS or something?) combined with a fragile print. You want as much filtering as possible for health reasons but you want to minimize air flow to minimize premature cooling or even the risk of "blowing down the print" as it were.

So... yeah. I would very much lean towards just having the intake/exhaust on the same controller.

Exhaust/intake fans generally aren't too important - materials like PLA that tolerate the air in the printer being replaced have very low emissions of potentially harmful VOCs and particles, and materials like ABS that emit lots of nasty stuff want the chamber air to stay hot, so having a fan replace the hot air with cold air isn't great.

If you do have nasty stuff in the printer chamber that you want to send out a window, then the exhaust fan is the more important one. Unless your chamber is totally sealed, an intake fan is going to increase the chamber pressure and encourage contaminated air to go out any gaps, whereas an exhaust fan makes the pressure lower inside the chamber, so encourages clean air to come in through the gaps, stopping contamination escaping. Obviously, this is only relevant if you've got a vent tube or filter on the extractor, as if it's just extracting into the room, there's no difference between it extracting the air and it leaking.

I guess maybe the use case for an intake fan is either if you've got a material that wants the coldest air possible, so want to swap the chamber air for outside air as quickly as you can, or if you've got the exhaust fan venting into a chamber where you're filtering the air without letting it cool down much, and the intake draws from that chamber. I don't think either of these are particularly common situations, though.

I've got a non-max SV08, and I just don't have an extractor or intake fan on my enclosure, and feed the extractor fan wire to my air filter.

You can wire the fans together as long as the exhaust is stronger than the intake, as you want to ensure negative pressure in the chamber so it sucks air in through the gaps, and not blow the out. You might need to add a resistor or something to the intake to achieve that though.

If you're going the route of a stealthmax, the v2 version has a servo controlled vent, original version it's manual. All filaments give off material you don't want to breath, nevermore has good info on this in the micro repo. Personally, I'd always aim for enclosed no matter what, the most I have in my garage is a box fan w/ decent furnace filters taped to it (works for wildfire smoke), I'd be venting outside if I had to setup inside the house.

I only ever had filtered recirc and exhaust on my enclosures, I'd rather keep it slightly negative to ambient air to try keeping the atmosphere inside the printer.