Unfortunately I don’t have a powerful modern PC, I run an i5-6400.
on my system the performance improvement is quite evident in some games:
Marvel Super Heroes vs. Street Fighter : on ymir is locked on 60fps while on beetle struggle a lot (since the intro, selection screen and in-game)
Sega Rally Championship : same story: rock solid on ymir, beetle can’t get to 60 (40-50)
uncapping the framerates I have a gain from 15 to 30 frames in ymir
Other games have less problems with beetle like radiant silvergun, but still ymir seems more stable.
All of this on my system with no shaders, full screen and integer scaling.
unfortunately I don’t have the means to do proper testing, just my “feelings”,
so take my word with a pinch of salt… 
transparent mesh seems to work well, I didn’t test any interlaced content yet.
Edit:
Just tried Virtua Fighter 2, deinterlacing works great and framerate is locked @60fps.
On beetle cant get to 60 (40-50) and no deinterlacing…