Claris is good. Shifting action has improved a lot thanks to trickle-down technology from the upper-level groups. Even 2300 and 3300 is better than my 12-year old Sora shifters.

However, as previously stated, cog spacing is different for 7s and 8s, therefore the shifters pull different lengths of cable per shift.

I once was building up a bike with 8s 2300 shifters. Unfortunately, I didn't have any more 8s cassettes in the parts bin but had two 7s cassettes. So I cobbled up an 8s cassette using one cassette and took one cog from the other cassette. The lockring did engage onto the freehub. When I tested it, shifting was sloppy from the second cog up.