I was playing Ultra Street Fighter 2 on the Switch yesterday, and my friend knocked my claw off when I was Vega! I was KO'd shortly after, so I couldn't tell if it affected anything.
Does losing the claw have any effect on Vega's moves?
Yes, according to Vega's wiki page, Vega is less powerful without it.
It takes exactly fourteen blocked hits for Vega to lose his claw. This reduces his attack range (and sometimes power) significantly, and prevents him from using certain Super Combos. Since Super Street Fighter II Turbo, Vega is able to retrieve the claw; in Street Fighter Alpha 3, he can lose his mask as well, though the effect is only cosmetic there. In SNK vs. Capcom: SVC Chaos, Vega cannot lose his claw. In the Street Fighter EX series, Vega may reinforce or recover his claw with a Super Combo.