I can't say that they will, or, won't be worth it, but I know how you can find out if they are. You have two bikes, yours and your wife's, make any of the changes, tires, wheels, what ever to one of the bikes. Go out for a ride, at the top of a hill adjust your speed so you are going the same, side by side. Maintain the same position, etc. and you will see which bike is faster. If you keep one of ht bikes the same, you can evaluate a series of changes to the other to see if they help.
Personally, working on your endurance so you can comfortably spend an extra hour in the saddle might be more practical. Being comfortable for 5 hours instead of 4 is like riding 25% faster for those 4 hours. Tours are very much about the journey rather than the destination. My $0.02.