Given that your Claris RD doesn't seem perfectly happy, I'd look at what model shifter you're using before buying a new derailleur. Claris uses Shimano 7-8 speed road pull rates, Altus uses Shimano 7-8 speed MTB pull rates, and Alcolyte uses a proprietary Alcolyte pull rate. Or perhaps you'd want to replace the shifter, too, to make sure they're all compatible.