My two pennies worth - Rail "code" refers to the rail's height, though not its profile, from foot to rail head in thousands of an inch. Code 332 = LGB and its compatibles e.g. Piko, USAT, Bachmann, all 332 thousands of an inch tall and are all flat bottom with similar profiles (there are some exceptions e.g. UK made Temmille). The different codes available in 45 mm track systems are there to allow better scale representations at one end, 200, or robustness, 332, at the other. Some makers use "bullhead" rather than "flat bottom" profiles, rare but beware. Different rail heights can be joined with the correct adapter but why create complications for yourself ? Settle on a rail code and stick with it. The code 332 based systems generally offer the widest range of off the shelf (set track) track layout options - switches, curves, crossings and slips (do you have those in the US ?),etc', so you avoid paying extra for "specials" to be made in the other types.
Curves & radii. Yes there are some who do not fear R1 curves and switches. Problem is they will limit your initial thinking and options that will inevitably impact on your future developments - don't do it. Sage advise I was given 18 years ago - nothing below 4 ft radius. If you are not inclined to create your own curves from flexi' track then I doubt straitening R1's out to get added value later is going to appeal. Having said that I started out with a load of LGB flexi and a single rail bender. It is a lot easier than you think to create the curves with the right tool, and again it gives you a lot of flexibility (see what I did there) in your layout designs into the future. I have a mix of flexi' and set track on my line with 35 yards of track in total. I do not have a large garden.
Inclines and control of live steamers - It is vary rare I come across a totally manually operated live steamer. at least on a meandering garden layout. Indoors or on those "racetracks" favoured by the G1 brigade (representations of mostly std gauge express trains on 45 mm gauge) is another matter. It is seen by some as a "right of passage" to be able to set one up to navigate a typically twisting line unattended. It can be done but can be a PITA to others sharing the line at a meeting, if not a downright hazard if it runs away or cannot be stopped for a blocked line . However, if you must and you have inclines to navigate, then get a geared loco like a Shay, Climax or Heisler. I have two that I delight in allowing to run free (at least on my line). Other loco type with good climbing ability, by adhesion alone, is anything that is an 0-4-0 or 0-6-0 configuration - all the weight is supported by the driven wheels.
OK that's my lot. Max.