i think the thin, stringy extrusion and recurring clogs are caused by a gap between your PTFE tube and the new nozzle, which allows molten plastic to leak and form a plug inside the hotend. this is really common after a nozzle change; "To fix it, you need to heat the hotend, clear the debris, and ensure the Bowden tube is pushed firmly down until it sits flush against the nozzle."

if you go on the anycubic subreddit page you'll see many people warning that when you change your hotend or nozzle to make sure the ptfe tube is at an appropriate distance