Black Vine - you can easily fit a second floor and make some nice gardens (especially if you have access to summerset limestone walls), but if you don't have ESO plus you'll run into the furnishing limit. For an Altmer you can get pretty creative in how you build this one. I made it into a wizard's study with a nice shady garden. Unfortunately there not a lot of services nearby.
Twin Arches has more horizontal indoor space and a nice patio, but absolutely no way to install a second floor. I made it into a bar/pub, because with ESO plus and such a flat indoor area theres a lot of furnishing slots for adding details. The view is also nice, but not as naturally appealing for an Altmer. This house is close to crafting services but no bank or writs.
As for other small houses that fit the accessibility criteria, Snugpod has access to everything but the house is rather meh, it does however have massive vertical space if you're creative enough. Humblemud has immediate access to everything except crafting writs, though its as appealing as a mud house can be (it's absolutely amazing though if you want to ignore the house itself and just terraform the outside using lots and lots of rocks and trees). Captain Margaux's also has access to everything but it's small and has no outdoors, and might not be suitable for an Altmer aesthetic.

Twin Arches - remember, that all redguard houses has flat top, so this can be easy 2nd open floor
Twin Arches - remember, that all redguard houses has flat top, so this can be easy 2nd open floor
The caution here is Twin Arches has a low skybox/invisible wall - so the flat roof is inaccessible. So disappointing.
If you have Imperial Edition, then Cyrodilic Jungle House (71k) would be the best option, coz it has biggest courtyard from that price category, but house by itself is pretty tiny
Actually, the Imperial Edition requirement for Cyrodiilic Jungle House and Domus Phrasticus were removed when Clockwork was released, at the same time they removed achievement requirements