i have used raingear/ catenary cut tarp, as well as poncho/tarp combinations in alomst all conditions possible, rain, snow, wind, ect.
I feel confident because of my experience in using either system. but there are a couple of things to consider.
with raingear/ tarp, you are going to need a pack liner to keep your gear dry, and deal with the fact that your pack will get wet, and probably gain weight in water. It is nice to be able to go out of your tarp at night, and set up your tarp with protection from the rain. but i often prefer a poncho tarp. because of a variety of reasons... less gear you need to deal with, less weight to carry, it provides weather protection for your pack, it has a ton more pitching options than a cat tarp. but when i first started using a poncho, i had a few hesitations like... having to stay under my tarp after i pitch it beacuse i dont have any other rain protection, having to set up/ break camp in the rain.
but in the end, i have learned ways to deal with the obvious problems of a poncho tarp, and often times prefer it.
comfort and confidence in a poncho tarp system comes mostlyy with experience.
as far as leg protection, I usually dont wear rainpants, weather i am using a poncho or rain jacket. i wear short running shorts, and just let my legs get wet, or wear a thin quick drying windpant.
i only pack the rain pants if i am in the winter or fall seasons, because of the temperature, so i dont ave to worry about hypothermia.
in the summer i have neve had a problem wwithout rain pants. another reason i prefer the poncho, it goes below the waist, and in most rains, my legs hardley get wet at all.