using a rim offset slightly different from oem?

That depends entirely on how much clearance there is. If the current rim and tyre is already pushing the limit then an extra 5mm can tip the balance and cause problems.

But for most purposes plus or minus 5mm is not going to be a problem. Fit them with the tyres and check at full steering lock and maximum suspension deflection. Bear in mind that a rear live-axle will also tend to deflect a little from side to side when cornering so you have to allow for that as well if your car has one.

Don't forget to tell your insurer: they absolutely must be informed of any modifications from standard.

That could be enough to cause clearance problems on some cars or maybe the wheel not even fitting over the brakes