Do you prefer the straight plus one bonus to every stat or the variant rule giving you a plus one to two and a free skill and feat?
...I think that I like the variant rule. Having a feat at first level looks pretty powerful. Any thoughts?
The feat is way, way, way more powerful than the +1 to all stats.
A feat is definition-ally worth +2 to your main stat, so a variant human has the equivalent of +3 in your prime stat and +1 to any other stat.
I hated the Human standard benefits since the start of the 5e playtest, so it goes without saying that I much prefer the variant.
However I don't think it's always a good idea to allow feats at 1st level. It depends on the players' experience, if playing with beginners I would suggest to avoid feats for the first few levels.
So I am in the situation where I hate the Human standard, and I think the variant is cool but not for low-complexity games. I need a third way.
For your third option, why not just pick a pretty universal feat to keep it simple and say every human gets that feat.
For example, +1 to two different ability scores, bonus skill, and resilient feat (+1 to any ability score and proficiency with that saving throw).