Hope you enjoy fishing the park as much as I do. I find myself up there almost every weekend too. You had quite a few questions so I will try to hit on them. Since you and I fish alot of the same water possibly the gear preferneces would be the same too. One of your questions is the more expensive gear worth it and my answer is yes, just not at retail prices
Here is what I use in the areas you are talking about
Big Thompson Canyon
Sage TXL 7'10" 3wt or TXL 7'10" 4wt depending on the wind and what I am throwing. Once Sept hits I use a 9' 4wt since the bigger browns get active and sometimes have to reach a little further to hit the other bank.
Big Thompson in the park
No wind = Elkhorn 7' 1wt for dries only no dropper (nudge nudge wink wink these rods are fantastic for the price and the shop is in Loveland on the way out of town to the park)
Some wind Sage TXL 3wt
Wind or using big dry / dropper Sage TXL 4wt
for what you are talking about doing with one rod to cover it all a 9'4wt would be a good choice. I prefer shorter for the Big T or small creeks in the park, but if you are hitting the lakes too then a 9 footer would be good . You asked about slower rods for rivers streams, that is a personal preference style type of thing but for me I find med fast to fast action rods work better since there is a lot of "flipping" and roll casting going on vs traditional full bore fly cast.
To bad I just sold my Sage Launch 8'6" 3wt this wekeend I would have let you try it out. I dont know if this breaks forum rules but I do have a 9' 4wt St Croix Legend Ultra on Craigslist right now that I only used twice.
---------- Post added at 03:38 PM ---------- Previous post was at 02:14 PM ----------
Also this guy is local and his website is a phenomonal resource for bugs and fly patterns. Really helps keep it simple.
Ive emailed josh many times and he is always helpful