Judging by the video, her guitar skills are fine. It's few seconds so, hard to judge, plus it doesn't seem to be a difficult song (part of song). I don't play guitar, but I listen and watch a lot of heavy metal/rock and to stay in japanese female bands, you can notice a difference :
Kanami from Band-Maid
Saki from Mary's Blood
They are pro and signed in major unlike Shoko's band. Again, Shoko's band is probably doing it as a hobby and with Shoko's contacts in the entertainment world, they had opportunities to record an album and play some gigs. Other members have probably a daily job (like most of musicians when you think about it, for 1000 people having music as their main job, there might be 10 000 people out there doing it on weekend only)
Another thing, in my opinion, they can't use Shoko's hoy body to attract people. It works with idols, but rock and metal fans want music quality first. Ai Shinozaki and Sayaka Yamamoto from AKB kinda use it (photobooks, magazine covers), but they belong to the idol industry. In the US, there are bands who hire hot female vocalists but they aren't taken seriously by the metal community (eg. Butcher Babies).
Nightwish was able to successed and still is a huge name in the metal world with their female singer thanks to their music and having an awesome vocalist. Another great band, all female band this time,
Crucified Barbara, proved that women can rock as hard as men (sadly, the band is now disbanded). So, neither of those two bands used the female body to sell.
In the second Shoko's video, it seems that some of the images are from her IV or JAV releases (the non AV intro of AVOP-210). And, I have to mention that the video made me laugh more than once lol. I really like her character.
