My waifu is from Touhou, which is very popular source. And to be honest, i really dislike most Touhou fans. I find their jokes and memes stupid, and the way some of them depict character, who is my waifu, can be really annoying for me. But after a while i learned to simply ignore and stay away from such things. It's not like anybody or anything can affect my relationship with my waifu, who is in my mind, one with me. That's how i see it - i already have her all to myself, and nothing can ever change that. It's not like by browsing stupid sites, reading stupid posts, and reacting to them in angry manner i could gain anything.
About "waifu competition", i find it pretty stupid too, for a reason i already mentioned above. I know there are/were some guys on TC who happen to have same character i have as their waifu. It doesn't make me feel jealous at all, my waifu is still mine and mine alone, while their waifus are their own, even if source character is the same.
Because my waifu is so popular, i never really experienced any lack of fanart. I'm not really into merchandise in general, but i have a daki of her(and aiming for a second one).
Also, even though i mentioned my cold attitude towards Touhou fandom, sometimes i'm still able to stumble upon really nice doujin (not H, those are always terrible), which gives me some new ideas and inspiration for my own fantasy.
Having either popular or unpopular character as a waifu/hasubando has both advantages and disadvantages anyway, so i'd say it's all about how you deal with them.