Track plates? Who drives what combination, what makes sense what doesn’t?

I drive VA/HA 225/40 18 8×18 ET45 rims on my C70 but the rims are still very deep inside when I look from the side on my fender that looks really stupid. I currently only have behind which 30s 15 per side but there is still 1 cm of air to the edge. I don’t want to fully excite it but it should have a healthy beautiful look. Who has experiences and recommendations and how to look t it with the registration at the TÜV? thank you.