General issue proof sovereigns would be those years bearing the standard sovereign design, in other words, most modern sovereigns. The most sought after ones (and consequently more expensive proofs) are those bearing a special design. Those years are 1989, 2002, 2005, 2012, 2017 and perhaps 2018 with its tiny commemorative mark. I started out buying BULLION sovereigns as an INVESTOR. I then switched to buying PROOF sovereigns as a COLLECTOR. When the price of gold increases I'll consider selling my bullion for a profit, but I'll keep my proofs which comprise of my collection. I hope this helps you.
I understand that's good advice it when I go to buy from my regular lcs I get to go through the whole bag witch contains about 75 to 100 face value and I always pick out the best looking coins for that part of my stack. To me it dont matter if they are modern or yesteryear coins as long as there in good condition!!!