Modern builders are using finer thread than the big makers of the pre WWII period. The standard size for production was size A and sometimes the finer OO size. YLI, a popular maker, now offers size 50 or 100 with 50 being the larger of the two and it is still smaller than size A of yesteryear. Modern makers are using Pearsall's Naples and Gossamer with Gossamer being the most popular and it is finer than the YLI 100.
The thread you chose affects the looks of the rod dramatically. You need to decide on the main colour and then a tipping colour if you choose to add tipping although one colour wraps can look great. The size you chose has a visual impact as well. Builders have to decide if they are going to lock the colour with colour preserver or simply varnish the wraps understanding that the colour will darken with varnish on raw thread. You have to make tests of various colours with varnish to understand what the finished colour will be.
I will say that larger threads are a bit easier to use and if you tip the wrap consider using a smaller size of thread for the tipping, this acts as a slight taper to the wrap and looks nice. Try to use the same amount of thread on each foot for uniformity and inspect the guides before you put them on for uniformity and finish quality. Often a few of the guides will require a little touch up before wrapping.
I prefer Size A thread with a smaller size for tipping, I like to use colour preserver and typically it takes 2 coats of CP and then 2-3 coats of varnish over the CP. The small guides on the tips get one less coat.
Whatever you choose, take your time and try to keep the varnish build minimal, less is more as it relates to varnishing guides. Remember the first thing someone sees is your varnish and wrapping jobs so a good first impression is paramount.