High Latency Spikes

My roommate recently moved out and we previously had an Xb3 modem I believe. I was connected via powerline and I was getting consistent gaming performance for online competitive with honestly minimal latency and no noticeable lag when gaming. However I switched to my own plan(1gb) and also ran an ethernet cable to my PC and my Internet speed/ modem test all come back with high speed/ no issues but man I have never played a game with so much rubber banding/ lag. This isn't the game server either as when the lag occurs I can't even open browser pages/load pages. It is significantly worse than the powerline adapter which is hard to believe since I live in an old apartment and who knows how the wiring is. What could be causing this? Should I just buy my own router/modem? It is unplayable even my voice in discord will cut out and sound like a robot. This probably happens every 30 seconds so it is unbearable.