No you don’t need an inlet fan/fans, yes you can, but you don’t have to. You still need an inlet, but most are “passive”, meaning they don’t have a fan. Most tents have a screened inlet, or two.
+1 on getting a “real” fan for the carbon filter, not an inline booster. I tried that, didn’t work, had to pay for an upgrade almost immediately. If you’re shopping online, 4” fans can be $45-75... check Amazon, $54 gets a decent one(now).
As far as where the venting goes, you don’t have to vent it outside. I ran my first run in a tiny closet, and vented into the bedroom. The bedroom had a window unit AC. You still want to exchange the air in that room too, that way you’re getting decent CO2 which your plants need.
Do research, ask questions, buy once, buy it right.