Old bike handlebar/stem upgrades

I bought a cheap (1995) Giant peleton just to see if I can get into roadbiking but the old school slammed style is proving not particularly comfy .

Its 1" threaded with 25.4mm clamp and a 110mm -17 deg quill stem which of course gives me a headache and back ache.

Is it worth converting to 1 1/8 threadless at 25.4mm clamp to get a positive stem angle or just go the whole hog and replace the stem + handlebars to the modern 31.8 oversize to improve choice ?

Are the various modern bars thicker or better shaped than old classic versions?