Bigjimknickers

2nd that on the stock servo of ours is still going, its in a different rig, but never died in the trx4, ran mine on an axe system with 6v set on the bec.
You should be fine but a stronger servo transforms performance allowing you to pinch into corners and have more power and control with a 7.4v or stronger servo
3s brings the rig to life, too fast go low range, still to fast, gear down on the pinion, but overall stock its amazing on brushless 😉

I still have the stock servo with heavier wheels, brass portal covers and brass pumpkin and has been fine for a couple of years.  No doubt it will break now I have said that 😜

I run a 11T Rocket 540 PLUS V2 brushed motor in my TRX4, with the two speed gearbox, which is about 2300kv compared to the 1850kv of the stock traxxas motor. I very much enjoy running it on 3S but have found for really technical trails sticking a massive 3S pack in the standard battery tray isn't as helpful as putting a smaller on up front. I just really wish they had made the front battery tray fractionally bigger so that a standard shorty pack would fit.

For a servo I've got a 32kg JX HV7032MG brushless model which I'm probably only getting 26kg out of as I've left the BEC voltage at 6.0V in case I fry the micro servos used to switch the gearbox and diffs.