Hi Jake amd welcome! I have been 'trying' to grow adeniums (or DR's) in the less than favourable UK since 2005 and have learnt most of my tips from Gweb, so I'm sure you will find our forum and it's members useful...more so the info from folks from your particular area. I'm very pleased with my plants, but just need them to hold a bud and flower for the first time.
Growing from seed is certainly possible for ppl with no previous knowlege of DR's, if I can do it, you will too!!! You just have to know a few special 'secrets' of germinating DR seeds...try a search using the search facility towards the bottom of the main forum page. If you don't get the answers from the posts is suggests, then by all means do a new post to hopefully get the answer you seek. There's nothing magical to sprouting them, believe me!
Seed grown specimens usually have large caudexes, but are obviously a slow way to get a big plant...in my case especially as we have a shorter/far cooler growing season than most. Sorry but I cant advise you on the other points you raised due to my location. I hope you enjoy the forum and your new hobby.
Gill from the UK.

Jake....

Welcome to the Adenium Forum. There is also a Cactus and Succulent Forum, and there is even more information posted there too.

Here's what I know about Adenium.

Seeds:
Easy to germinate...and FORGET the photos of flowers! Adenium doesn't bloom to make flowers like photos show. Selected, superior varieties are always grafted onto an under-stock. 99% of all seed-grown plants will produce common, pink flowers of varying merit. NO seed seller can guaranty/predict flower colors, or shape. If they claim that their seeds are superior, and will breed true...they are full of crap! Plenty do, and they are crooks.

mgonline...sucks!
Top Tropical...questionable reputation.
eBay...a crap-shoot, and YOU take the risk.

Try:
Durham Botanicals/Bonsai-style Adenium
Lucky Sumo Adeniums
Living Stones Nursery
Miles2Go
Cactus King/cuttings
Bonsai Collectables/succulents/caudiciforms/Adenium...etc. (Very nice plants, and owners)
Desert Theater
Ted's Exotic Cactus and Succulents
Arid Lands Nursery
Tropiflora Nursery
Shoal Creek Succulents

Keep in touch. This is the place for good information.

I live in NYC, and it ain't Arizona. Adenium are no more difficult to grow than any other juicy succulent. If you can grow a tender succulent, you will do fine with Adenium. Winter culture will be the problem, if any. Keep, cool, bright, dryish, and take cues from plant. Start to gradually water when new buds show.

Hope this will help.

Frank
Bronx, NYC