I used to have a slider ESC as well 20 years ago!
(damn those years fly by)
Had it in a old Tamiya!
Higher KV = More RPM so more top speed.
Lower KV = Less RPM but more torque (off-road)
For heat problems i find that my 7.5T gets hotter then my 4.5T since i need to crank up the boost/turbo alot more with my 7.5T to get the speed i want.
For starter i would go for a 10.5T. Hope this helps and enjoy