Volvo 480 Club Europe

Are 7j wheels too wide?

If you are going to fit 205/50-15 tyres 7J would be perfect. Even the standard 195/55-15 will fit.
I have 7J rims on my V70, factory fitted with 225 width tyres.
See also: https://www.tyres-pneus-online.co.uk/ty ... dvice.html

Make sure the rims have the correct offset (ET)

what should the offset be if I use 7j wheels?

You'd probably want an ET of around 30;

See here