strenth vs. endurance..... have to choose ? How much to Eat ?

Aztec

By FAR the strongest factor in all of this is genetics. Some win, some lose. Carrera, you clearly are a winner if gaining muscle mass is the game. Most are losers by that measure. Gaining muscle is very hard work, and close to impossible for many.

All that said, maximize your chances by doing exactly what Carrera suggests above. SQUAT 20 reps. Toss in a few other things like deadlifts*, some form of press, and some form of rowing or chinning/pullups, done for 8-12 reps. That's all you need aside from abs and calves (if you care about calves, that is). If you struggle to gain, make sure you aren't overdoing the lifting volume. One or two hard work sets after enough warmup should be all you need. Way too many think that because they aren't gaining, that must mean they need to do more. I'd bet that's the reverse of what's needed in most cases.

Count on needing to gain a lot of strength if you want added muscle. If you can squat 135x20 now, when you get to 225x20 you should be on your way to seeing some real improvement.

A big excess of protein is a waste. You can only use what you need. Any more just gets burned as fuel rather than for constructing muscle. Protein is expensive, so don't bother overdoing it.

I should speak to my credential here in the interest of disclosure. I was (am) one of those thin dudes. 38 yrs, 5-10, 160 lbs, reasonably lean. I would weigh 145 if I didn't, or hadn't, lifted. The proof is in my skinny calves, forearms, and neck -- the telltale areas that are so hard to grow. Until a few years ago when I injured an already "iffy" back, I squatted and deadlifted. That's where the results were. Now I avoid that, and worked up to dips with +100lbsx7 reps, chins with +55lbsx3. Returning to cycling 10 months ago returned those lifts to lower levels! The important point here is that I (and most others) gain(ed) very slowly. Once you've been lifting for say 3 months, adding a pound or two to the bar every month is decent progress -- building muscle past the age of 20 is a slow, deliberate process of microprogressing.

* Get professional instruction, from a quality source, not the dingbat trainers in a commercial gym. Try Stuart McRobert's book titles something like "The Insider's Tell All Handbook to Weight Training". He has written 4 books, all are outstanding (the best, actually).

Carrera

Thanks for the positive comments and post.
It might surprise you but I have very poor genetics for weight-training so it took a long time to gain a degree of natural strength and develop a normal physique. Some bodybuilders are lucky since they can do lots of work on the road-bike and hold on to their muscle size in the gym as well.
However, in my case, if I do too much cycling (or even too much weights) I tend to drop too much bodyweight (for my own particular preference) and overtrain easily. I'm basically an ectomorph and have very little in the way of mesomorphic genes that are so common to natural athletes.
Let's not forget, though, that when we know how to train specifically for our purposes, we'll all all make progress. Knowledge is fundamental. Persistance is also very important.
With regard to weight-training, guys in my own area make the mistake of using too many machines and not doing squats (since they're hard work). Plus they talk all the time and don't train intensely. Or they make the mistake of doing isolation movements and wasting too much energy on little muscles. Hard work, on the other hand, always pays.
Weight-training and cycling are two different sports but if a cyclist feels he (or she) would feel better with a few extra pounds, as a recreational bodybuilder I guess I can offer some reasonable advice. However, when it comes to increasing fitness or hill-climbing skills, I'm basically a beginner and am hoping I'll learn something as well.

Aztec

I'm not sold on your 'poor' genetics. Almost everyone struggles to gain at all. Only the very young and/or gifted have a relatively easy time of it.

It's funny -- I rarely come across anyone who thinks they have even average genetics. It's kind of like how everyone thinks they are an above-average driver, just opposite of that! I KNOW I have poor genetics!