Here's how I play, and I don't feel overpowered AT ALL. I'm currently at lvl 23, about 55 hours in, and I frequently have to bow out of boss fights and come back later.
Difficulty: Adept.
Playstyle: All out warrior using no spells at all.
Weapons: I love 2 handers and bows, and I love unique weapons, so I'm sporting an un-enchanted Skyforge Steel Greatsword I made myself. I also carry a Dwarven bow with Soul Trap that I found. I won't keep it, tho, I don't like the look of Dwarven gear so hopefully I'll be able to make myself an Ebony one soon when my Smithing is up to par.
Armor: Steel Plate, again, homemade. Best looking armor in the game for my character, and I doubt i'll wear anything else just to bump my armor rating.
Skills: Two Handed, Block, Archery, Smithing, (Sneak, just because I snipe with my bow and Sneak levels unintentionally), and then I might start to get into Alchemy or possibly even Enchanting soon as I'm running low on potions and I want to be able to name my weapons.
I've played the way I want to play, exploring with no end goal in mind, taken perks here and there when they seemed relevant. For instance, if I felt like I was starting to have troubles in fights, I'd start picking a few Two-Handed perks to boost my combat. If I'm doing good in combat, I'll work on my smithing perks etc. I don't train skills, I only get what comes naturally, and I don't power-boost skills like Smithing either. When I have enough ingredients I make some cool stuff that I may keep, may give to a follower, or in some cases I sell it if I need gold for something specific. My guy loves to Smith, and whenever he's in Whiterun, he'll hang out at the Skyforge and chat it up, smith some cool stuff etc.
I don't power-loot either. I only take nice stuff that can fetch a good price, or that I want to give to a follower or possibly use myself. I don't travel back and forth between dungeons and cities to sell every bit of loot I find. If I'm at my max capacity, I'll be even more selective in my looting. I don't just head to the nearest city and sell it all off and go back for more.
I don't fast travel, ever. Twice have I used the carriage service because I role played my character. He had traveled around the mountains fighting all kinds of critters for about a week, and he was tired, so he took the carriage home.
Everything I do I do from a role playing perspective. The key is not overpowering myself for Adept skill level. That lets me put perks in non-combat skills, and as a result I've developed a real and whole personality for my character. He's a self sufficient guy who lives off the land, only takes what he needs, and always give a few coins to the poor. I have a humble abode in Whiterun with a few nice looking swords on the walls, and about 2000 gold in the chest.
That's it. Nothing fancy, and I'm enjoying the hell out of it! I don't know that it's self-gimping, but it surely has balanced the game out nicely for me, and I feel real good about being able to use various skills without thinking about under-leveling or over-leveling.
Your overall approach is very similar to how I play, Phoss.
I learned, the hard way, in Oblivion that FT and power-looting svcked the joy out of the game for me and turned into a numbers game. Ditto powerleveling skills or creating a "plan" for my character.
I play my character in the moment, I never FT (haven't used Fast Travel one in Skyrim), and I don't pick up dozens of weapons or armor. I try to focus on gems, small items, components, other valuables that I could imagine putting in a medium-sized pack.
For me it makes the game much more enjoyable and balanced in terms of difficulty, too.