I just checked out some of the merch from that line. It didn't look bad, quality-wise, but I can't work out if it's worse to go around in public with a big-titty anime woman on your shirt or a petite loli. Definitely nothing I'd want to remotely be associated with, even if they were my favourite vtubers.I thought some of the omocat Gura merch came out looking great, but I just wouldn't be caught dead wearing that stuff in public so in the end I didn't buy any.
Gura knows our struggle though, when she released her shirt last year she said that she'd tried to go for a design that wouldn't be blatantly "anime" so people could wear it in public. Hopefully she'll release more merch with the same philosophy at some point.
The only way I'd see shirts and the like working is making the merch so abstract that an average person looking at it wouldn't associate the shirt with Japan or anime, while people who are fans would recognize it and know that you're a fan of Gura or Pippa or whatever. But even then I'd be wary of getting the merch because most anime fans are spergs and I don't want their attention.