Probably getting to point that you'd be better asking these on some of the free flight forums as suggested. That said...
...I'll give MY view.
Rounded nose spars. Just what it sounds like. Round off the top and bottom LEADING corners of the leading spar. Start with a square 1/16 spar and round two edges. Meant to improve airflow and it doesn't take much. Not sure how critical it is, but at top levels of competition, you start seeing things where competitors try to reduce drag by such actions to the leading edge. Before there were so many carbon fiber spars in SO, some of the designs had triangular shaped leading edge spars for the same reason.
Tapering on the winglets is to reduce weight. Hitting weight on an LPP is very doable, but not if you don't pay attention. Less stress at tips, so need less material. You do it by taking a sheet of material (the length of the tip spars) you plan on making the tips from and carefully sanding in the desired taper on one face. Obviously along the grain. Then you cut out your tip spars on a taper, a jig of some sort is real handy there. You end up with triangles of waste balsa with taper in the wrong direction between your tapered spars that you just discard.
Prop making. Yes there are programs to figure out what angle and ideal diameter to use to form a prop to a reasonable approximation of a helical prop. While a given diameter can be used for a range of prop pitch/diameter combinations, there are limits. If you don't have a gallon jug, do you have a small pail of similar diameter? Could you get some tin from the hardware store and form your own cylindrical (or actually more accurate, a frustrum) form? Alternatively, if you have a bunch of spare balsa, you can make a true helical blade form pretty easy.
Rib templates are pretty easy. I like to make them from Mat Board, the cardboard backs of pads of paper can be good. I had a long explanation, but again, Indoor News and Views is your friend. See page 87 of https://indoornewsandviews.files.wordpr ... f-inav.pdf
I like to reinforce the curved edge by soaking it with CA and wiping off the excess. If you are careful it will last a LONG time. As to the exact curve, for that plan the recommendation is a simple arc. It works.
If you haven't already, read the Hobby Shopper
and the “My Way” Penny Plane construction
on that same link. INAV has a wealth of knowledge.
Hope that helps,