I played Hofners, mostly 501s, for decades before I switched to my Jack Casady bass.
I always used flatwounds on my Hofners. From the early 1970's to about 1990 I used Pyramid Gold strings when I could find them. The Hofner branded flats are made by Pyramid, but they are not Golds.
The Golds had the warmest tone, so deep as pliable, a dream to play through my Ampeg B-15N .The Hofner version, like the Labellas, had a more metallic sound, and brighter ,and were stiffer. The Labellas were too bright and stiff for me. Others may disagree.
I gave up on the Pyramid Golds after I purchased several packs each with either dead E strings, or mis-wound, untunable strings. Poor quality control. I met with the people from Thomastic-Infeld (USA) and showed them the problems with the Pyramids and the Labellas. Eventually the Thomastic-Infeld flat Jazz short scale came to be. I know you didn't ask, but I found their quality control to be excellent, as are their strings, which sounded great on the Hofners.