Deadmans hand, while a gresat set and the main one I play is in no way a detailed set, much more a fast play set. Desperado is a bit more detailed, and I believe six gun sound is more detailed still. I say believe because I own but have not plsyed them.
Another approach that may fit what you are looking for is the RPG Aces and Eights. Again i own but have not played it, but it look quite detailed.
A kknown problem on TMP for a rookie is when you aslk for rules recomendations we tend to offer our favorite rules that may or may not actualy meet your wishes. Deadmans hand is likely a case in point. They are a very fun fast play set. Just did a con game with them thjis weekend with 8 people in the game and everybody had a great time. But detailed they are not. All six guns are the same. As are all other weapons in thier own groups. A rifle is a rifle. No hoit locations, just under fire and when you get to many of those you are out. But, you can gain back from hits, something one noirmaly does not do from a hit bya real .45 colt. So really good game for what it does, but perhaps not what you are looking for.
As for scale i have found a lot more variety in the 25/28mm Stuff. If everybody matching size is important do a little research as there are large and small figures out there. I have at least a few figures from most of the companys and use them all, but i have not gotten any from the know larger ones yet. I may get a few soon and use them as a few larger fellows as are mentioned in many western books. But not more than a few/.
For buildings, have settled onm MDF from mostly knuckleduster and Sarrissa. These best fit my needs. But I have Old Glory, 4ground Architects of war and several others. I like all of them, but 4ground are very expensive, and the resin ones tend to get broken up if you travel with them. As I take mine to cons this is a big consoideration. If you con travell then that is less of a problem, unless you have butterfingered friends.
If cost is a consoideration, I think Sarrissa isabout the cheapest and the esiest to build forthe buildings. Desparado is probably the cheapest game at about $15. USD For figures old glory are thecheapest, but you get a lot of repeats. Old Glory also has the westwind line whicxh while not cheaphas both mounted and dismounted versions of the same charecter. I have some of them and over time will own them all.
A big consideration is what you want to do. if it is mostly gunfights, thena half dozxen figures rules and a couple of buildings will get you going. I have become obsessed with doing a full town so I have over 30 buildings ands over a hundred figures. I dont think most people have banjo players ands cancan girtls but they are out there and can really add to the look of a setting if that is what you are after.
Please ask any and all additional questions here. you will get replys, some of which wont quite answer what you ask but will help narrow your search. And some will give you just what you are looking for.
happy gaming
Owen