I read the manga first, and I personally prefer manga Merlin. (Maybe it's my unusual taste at work? I've noticed I have a tendency to love certain "garbage" series while feeling lukewarm about a couple of fan-favorites.)
In any case, I think "lech(?) who wants a harem of girlfriends (bonus if demihuman) and knows he's super hot ... until actually no, wait, he doesn't know how to handle this attention!" makes for a more interesting character than "dense humble isekai protagonist #194738 who hates standing out."
He might fantasize about a harem (because it's a Certified Isekai Trope and he's a "Healthy Male") But he's not getting into creeper territory until he starts oogling people's bodies. If he treats his fantasy harem as human beings instead of curves and holes, I don't see the problem with him wanting multiple partners as long as they all consent.
(I know a fair few people in open relationships. Also, men are allowed to be asexual/demisexual and there's nothing unhealthy about it.)
I approve of God's kaomoji ( *｀ω´)
The manga gives both of their personalities some levity and energy that I appreciate.
I also appreciate that Merlin has a lot of trouble holding back his strength. He breaks writing utensils and might hurt his friends without meaning to. He sealed himself out of necessity, not just to blend in. Then he regrets it because of subsequent events.
