What sort of impression do you get from these names? What sort of traits/personality do you imagine someone with these names to have? These are the last two names on my list and your responses will really help me settle on one for sure.
Thank you! 
Ieuan has a very specific personality to me just because the ones I know have very similar personalities - sporty & loud. [name_m]Ewell[/name_m] seems quieter, maybe a bit shy, the sort of person who likes to read. FWIW, I don’t think someone’s name defines their personality. I prefer [name_m]Ieuan[/name_m] as a name but that may be because it’s more familiar to me.
Ieuan sounds really interesting. I quite like it
Ewell reminds me of both the place near where i live and the character from To Kill a Mockingbird
I love [name_m]Ieuan[/name_m], the only one I know is called [name_m]Euan[/name_m] though which I like a bit more but I think both are great names
Ewell is probably the one that would be most understood in the US. If you’re in the US, or travel to the US, I would suggest explaining how to pronounce his name by saying “[name_m]Ewell[/name_m], like Yuletide.” This makes me think of a winter baby. It’s pretty common for people to give their child the middle name [name_u]Yule[/name_u], [name_u]Noel[/name_u], or [name_f]Noelle[/name_f] if they’re born in [name_u]December[/name_u].
The majority of people in the US (and maybe other areas, but I really don’t know) will initially pronounce it ew-elle. As long as you’re ok with that, this one is definitely my vote!
The only [name_m]Ieuan[/name_m] I’ve ever come across pronounced it YOO-un, but the pronunciation of both names on your list wouldn’t be difficult for someone to pick up once corrected - and I reckon you would end up needing to correct a lot pf people if you don’t live in [name_m]Wales[/name_m]. I think [name_m]Ianto[/name_m] would be a sweet nickname for [name_m]Ieuan[/name_m], and I prefer it to [name_m]Ewell[/name_m], which I’ve only ever known as a surname and the ‘yool’ pronunciation reminds me of [name_u]Christmas[/name_u], so would sound odd to me on a non-winter baby