Copper wire vs Tin wire (same LOSE? O.o)

The wiki is using the old value, tin cable has had 0.2 EU/block loss for years now.

Your best bet is to connect all the solar panels around sides of an LV-transformer then up transform using it so that there's as little loss as possible. Remember to use copper cables if you do choose do this (as it's now at 128 EU packets), and down transform with another LV-transformer if it's going into a batbox. Ideally there'd be an ULV-transformer for doing the same process but still having 32 EU packets, but there isn't so unless you put the solars all around a batbox (which is another viable solution, although uses more tin and redstone compared to transformers), it's about as good as you're going to get.

It's quite situational depending what you have around. If there's lava near by, then geothermal generators can be quite good. If there's a deep river or ocean, water turbines are good, so long as you have the iron (or carbon fibre) for the rotors. If you're quite high up, wind turbines are very good, but quite a lot of power can be lost if you're not. Solars are windmills are good for passively generating power over time, but are normally too slow for much else without power storage. Eventually you'll want to aim for nuclear power, but that's later game then you are at the moment.