I would like to get a good quality RC drift car for indoor usage and add fpv to it.
Thinking about 1/24-1/28 size but really not sure what brands I should look into and what upgrades I should buy right away.

In the last 4 years, I have build race drones, so I know how RX/TX and VTX works but how no idea who makes good quality stuff.
I use flysky for my drones, and that's a budget-friendly brand.

Is flysky the way to go for RC car controller or are there any better options?
I see radiolink rc4gs gets some decent reviews vs the flysky gt5?

Since I would like to order from banggood, there are some wltoys options like K989 + K969 + A252
And the more pricy sinohobby with the Q series like Q5 and Q7.

I checked out Beavers Hobby on youtube, and he shows a lot of different upgrades to both sinohobby and wltoys cars.
Seems with all the upgrades needed to wltoys, it's better to go with sinohobby Q5/Q7 instead?

1. Is sinohobby Q5/Q7 worth the extra money? Or is wltoys the better options?
2. Is flysky gt5 or radiolink rc4gs a great option or anything better around same pricetag?
3. What upgrades is recommended to do right out of the box?

1. Yes for the Q7. It's competition level car with tons of adjustability and good (also grease filled) shocks. However this car is a bit soft in places due to adjustable linkages so if you are unsure whether if you will crash it hard, WLtoys is more durable car.

2. They are the same in term of control. However RC4GS now has telemetry so you can monitor battery voltage and signal strength.

3. For Q7, it's rather fix than upgrade. Change dogbones to metal from WLtoys (they are 9mm long and will fit Q7 better) and change the wheels to 1mm offset or more so they won't rub against suspension arms.
After that you can fill the shock with gear diff grease, medium viscosity. I use no. 30000 from Kyosho and it gives me very good dampening and reboud with stock springs.
Tyres also play a big role. Choose them according to the track surface and it'll fly (hopefully metaphorically and not literally off the track).
A good aerodynamic body will also help. I personally like Kyosho Lexus SC430 GT500. The body is slow to turn but my Q7 is darting a lot in the corner (I need to check setup again) so the body compensates it nicely.

ps. You've given me an idea for Q7 touring guide video. I forgot I've never made on on this topic before. Thank you.