Firstly, I have no idea who Prince Philipp is. LOL.
1. I think it's okay, but the -lip part sounds very ugly to me. Kind of like Caleb or Jacob. I could never get into those names because of the B at the end. It's such an ugly way to end a name. I pronounce it FIL-ip. I've never heard FEE-lip, actually.
2. I know several Philips, but I could never ever remember how they spelt their names. There are way too many possibilities. Most of them are around my age, 19/20, but I know a few younger ones, too.
3. I don't think it'll make it to the top 100 in the next few years or so. I also have no clue about the spellings. They still confuse me to this very day.
4. I like Philip the best, because it's the only one that doesn't confuse me. The one I like best ultimately is Felipe, though, but I guess it can't be counted as a spelling variant. Phil is okay as a nickname, I guess. I associate Philly only with the city and don't really see it as a name.
5. Jesus, YES! I always break out in cold sweat when sometime tells me their name is Philip and I have to write it down.
6. I think Homer Philipp flows pretty well, Richard Philipp not so much. But they're both good combos.
7. ROFL. I had to look it up. "Friend of horses." I'm trying so hard not to view it ambigiously, but I don't succeed. I also don't like horses, so it's probably not a very nice meaning for me.
8. I think Philippus is nice, mainly because it doesn't end in -lip.