Yes,the bike will be lighter and quicker to steer with the narrower front tyre.....it will be more ''agile''.
Regarding the brakes...are the shoes adjustable individually like on my Urals?
If so,chalk the shoes and apply the brakes to a rotating wheel then look for full and even chalk removal....or adjust and repeat until so.
If they`re not adjustable,maybe you can shim the feet of the shoes to compensate.
Or maybe you just need new shoes.
Also use a good brake cleaner solvant to degrease the drum.
A heavy duty brake cable may also help...it did on my 650 Ural.
I'd only waste my money if I didn`t spend it on all my bikes......