Thoughts on your shortlist:
[name_u]Tristan[/name_u]- I [name_f]ADORE[/name_f] this name. Absolutely love it. Not keen on [name_m]Felix[/name_m] or [name_m]Malachi[/name_m] as middles options with it though.
[name_u]Arlo[/name_u]- typically I’m not a big fan of this name, but both potential middles bring out something very earthy in the name. [name_u]Arlo[/name_u] [name_m]Forrest[/name_m] I think is especially nice.
[name_u]Jude[/name_u] [name_m]Ezra[/name_m]- a bit biblical heavy, but a perfectly usable name. I think [name_m]Ezra[/name_m] [name_u]Jude[/name_u] sounds slightly better.
[name_u]Everett[/name_u] [name_m]Isaiah[/name_m]- another perfectly usable name. I’m not enchanted by it, probably just because I know so many Everetts and Isaiahs, but it’s a name that won’t end up feeling dated.
Thoughts on your longer list:
[name_u]Beau[/name_u] [name_m]Malachi[/name_m]- works great, I like this the most of the combos you are considering with [name_u]Beau[/name_u].
[name_m]Otto[/name_m] [name_m]Peregrine[/name_m]- I like the punchiness of [name_m]Otto[/name_m] with this softer middle. Both old names that feels very fresh. Really like it.
[name_m]Rafferty[/name_m] [name_u]Jude[/name_u]- a good combo but I do think switched around to [name_u]Jude[/name_u] [name_m]Rafferty[/name_m] sounds slightly better and puts [name_u]Jude[/name_u], which is a clear favorite of yours, back into a first name position. If you considered [name_m]Rafferty[/name_m] as a middle for [name_u]Tristan[/name_u], it would be my absolute favorite name combo on your list
[name_u]Rory[/name_u] [name_m]Elijah[/name_m]- this is a sweet name that reminds me a lot of other pairings on your list like [name_u]Everett[/name_u] [name_m]Isaiah[/name_m]. In fact [name_u]Everett[/name_u] and [name_u]Rory[/name_u] would be a great sibset.
[name_u]Keegan[/name_u] [name_m]Evander[/name_m]- not a huge fan of [name_u]Keegan[/name_u] but this combo does work well. I’d also recommend playing with names like [name_m]Keiran[/name_m] and [name_m]Killian[/name_m].
[name_m]Bodhi[/name_m] [name_m]Atticus[/name_m]- I have a lot of reservations about using the name [name_m]Bodhi[/name_m] that I won’t get into, but even putting those aside I think this is my least favorite combo on your list. [name_m]Atticus[/name_m] is a great middle but doesn’t suit [name_m]Bodhi[/name_m] at all.
[name_m]Felix[/name_m] [name_m]Henry[/name_m]- great classic name with a little more vintage and underused charm then some of your other considerations. It almost seems out of place with it’s lack of a biblical/Hebrew name somewhere in the mix.
[name_m]Wilder[/name_m] [name_m]Orlando[/name_m]/[name_m]Horatio[/name_m]- with [name_m]Wilder[/name_m] in the first spot, I prefer [name_m]Horatio[/name_m] as the middle. If [name_m]Wilder[/name_m] were bumped to the middle though, than I would lean towards [name_m]Orlando[/name_m] (as in [name_m]Orlando[/name_m] [name_m]Wilder[/name_m].) Honestly though any of them is a solid combo and are among your most exciting considerations.