I have to admit, that Popeye mockup looks pretty good. Although there would likely be a lot of sprite flicker when Popeye and Bluto are displayed along the same scanlines. The bottle-throwing Sea Hag could also be a source of increased flicker. Still, very nice.
Actually flicker shouldn't be worse than the others. Here is why, if you care about those technical details.
Pengo uses the same hardware as Pac-Man, which means 6 sprites total (3 colors each). Since I usually use 2 CV sprites to emulate arcade sprites, that give us 12 sprites. So in the very worst case we can get sprites flickering at 20Hz, which isn't that bad. Actually that is exactly what we get with Pac-Man Collection.
For DK Jr, it is harder to give an exact number, but we can expect about the same amount of flickering as DK, which is in the 14 sprites range in the very worst case (actually I suspect DK Jr should do a bit better than that, as we don't have something like the rivet stage).
Dig-Dug is even harder to predict, but I can tell you that the later stages can get really busy with enemies. Considering Fygar's fire and Dig-Dug's air bump, I would say perhaps 16 sprites worst case, which is 15Hz.
Now Popeye. Both Popeye and Bluto would use 4 sprites in the same scanline maximum. Another 4 for the Sea Hag. So 12 so far. Then we could have a couple more for help letters. So again in the same range as the other games. Now, we need to take into account that those are worst case numbers. Most the time Popeye isn't the same platform as Bluto actually. And the Sea Hog only shows in stage 3.
For all the other games I can offer the same option I am including in DK, using single sprites for all enemies. That reduces flicker quite a bit, though making the game less colorful. For Popeye I don't think that would be a good option, as all the characters must be recognizable and hearts, notes and helps are already single color.