Just My Size Women's Full Zip Slub Hoodie Plus Size

What would you recommend for a busty woman that normally wears 18/20

i wear a 1x not sure if i should order a 1x or a 2x

Is the material thick? I'm looking for a thin lightweight one

looks uncomfortably tight on forearms. is it? appears that it could not be worn with long sleeves. normally 2-3x, will buy 4x.