If you have stable 500w from solar panels you still need a bigger power supply at least a 750W i personally would still opt for eth mining with some powerful gpu
yes but will this be long term? in August there will be merge of ETH 1.0 and ETH 2.0 to ETH 3.0
The end of ETH mining isn't the end of crypto mining but if ETH mining is your main aim then do not build any mining rig because Ethereum is surely going PoS algorithm by August of this year.