Being a newbie - I think thumb notches should be out until you learn to strop well - it is a fast way to either drop your blade on the floor while stropping or cut your strop as there is a bit less to hold.
I think jimps are nice but not necessary - any standard straight that has a good neck (if that is the right termininology) will work well and allow for a balanced hold.
I also think shoulderd blades versus shoulderless are best when beginning and learning to hold a straight proper.
This is strictly speaking from my own experience and each person has learned differently on different blades with or without success. thats my disclaimer :)
andy