Hi Thunderwow and welcome to the forum.
I know Seaford and like you launch mostly on East Sussex beaches (Bexhill, Cooden, Hastings etc) and horribly sharp, shingly, steep things they are as you know.
Whatever you use you will need the wider sand/beach wheels rather than narrow small pneumatics which are crap on our local areas.
You should be fine with transom wheels with what will be a very light boat. Going down is easy but coming up (depends if you are alone or not) will be a struggle with any weight. We bring the bare boat up and then the engine (on a wheeled trolley), fuel, Pelicase etc separately.
It can be pretty choppy coming back in at Seaford if the sea changes while you're out - noted from your info you list an electrickery OB (
) - have you got a petrol OB too?