If you want a reliable 30mph at 48v I would suggest on saving up and getting a 48v 1600w brushless motor with bracket and controller combo get a t8f rear sprocket and chain you will see what you need and more no problem.
There's also the dualtron hub motor that can fit the rear with a little work and that gives you room to put the controller in the motors place and use the full battery box for batterys there's a thread on here with a razor built with one it's the more expensive choice few hundred dollars but the finished ride will be sweet if you pull it off
Battery wise I used Lipo and balance charger to get as much in as I could with lots of output power.
The motor suggested at 16s will see this scooter go over 45mph so I would suggest getting a front brake on there the drum on the rear copes fairly well even with water and dirt so a disk upfront is needed first I'd suggest but if you can get a disc setup on the rear and it does work fairly simple even with the standard wheel there's a disc to threaded hub adapter for mtb that does the job.
The front need a disc wheel as there's no way if getting a disc to mount to it if I remember correct the narrow wheeled razors come with a narrower front fork of 120 or 125mm vs 135mm of top of my head so it might be worth getting some mini moto wheels and a front fork from a big tyre scooter along with a front mtb disc conversion kit and have bigger tyres brakes all round.
The 4×3.00 tyres are much better over the bumps at 8psi the ride is decent nice and smooth can handle gravel roads in comfort depends on where and how you ride the skinny tyres have a better range on tarmac but there's big off road tyre, wet tyres or a slick in the larger sizes where as the 2.50 skinnys don't have the choice there's lots of avenues to go down.
The kuberg is a beast power wise it only does 35mph but it pulls like nothing I've had even up rocky inclines full throttle and the front end comes up few seconds I'm flat out easily keep up with a 125 off road at low speed, temperature is a problem though when it's cold the performance drops the packs need to be kept warm charged then instantly used and abused to make sure I get maximum fun, at lower power levels it's not as much an issue unless your pulling the cells limits or big amps at low volts the kuberg runs 13s10p 54.6v and 220amp gives 12kw max hot off charger it then drops down to 9kw when the batterys flat, enough to keep the front wheel on the ground and add 2 or 3 seconds to flat out.