I have used Pledge on my bikes for almost 20 years. My brother (who in his younger days was a sponsored bike racer) used Pledge so I always figured if it was good enough for him, it was good enough for me. He treasured his bikes!
I use car wax once a year on each bike frame. Early in the season, I take the time to do a thorough wax job (think bike wax here - forget that bikini wax thread....) on each bike. I think it starts out the season with a good, protective coating on the bikes. I use Turtle wax, but I don't think the brand name makes any diff. I have a carbon frame, an aluminum frame and a combo carbon/al. The wax and Pledge seem to work on all them.

I love the nail polish trick. Used it many times. My good road bike is yellow. I found nail polish to match. I've touched up the frame with it, and, yes, painted my nails to match. All in good fun.

Back to frame material - I've ridden steel, aluminum, carbon fiber, and a combo aluminum/carbon. Each has some advantage. My mountain bike is aluminum; very cost-efficient and I don't ride off-road enough to justify spending a large sum on a mtb. My road bikes are aluminum/carbon and totally carbon. I love the carbon fiber. It is responsive and it is comfortable! Not quite as responsive as steel, but for me, the trade-off in comfort is absolutely worth it. I know, you can't fix it if it cracks, but the likelihood of that happening is so slim, that it is not a factor.
Never have ridden a titanium bike so can't have an opinion on that.

It all boils down to personal preference! Just ride and enjoy!

annie