Marine:
Reply 1997 & Coffee Prince are two of my all-time favourites and they both fit the bill (although I'm biased) BUT they both do have dramatic moments that either separate the leads for a bit (not for stupid reasons) or have fights/tension (again, not for stupid reasons), so there is some drama, which, in both cases, I think was necessary & executed well. Any drama with Park Bo Young is usually quite good with the fluff, but I'd really recommend certain Family dramas/longer dramas in general for ~advanced fluff (aka from strangers to dating to marriage,where skinship and stuff of that kind is less off limits and the leads are understood to be doing everything in a relationship rather than just like innocent PG kisses). The best I've found of that kind is Glorious Day with Park Se Young (so, so underrated) and Five Children with Shin Hye Sun.
Never tried a family one. I love when they go through meeting to marriage with all that. Playful kiss was what got me into drama and then anime and manga, and while now I think it's kinda...ick....I did like that it had them married and a bit after that. I still like when they're together for a while with the sweet moments. A family drama would probably be up my alley.
Also I did like coffee prince. Thinking about reply 1997 but I'm terrified to get on the wrong ship. I just did that abound now I'm so bitter and angry. Screw you "Let's eat" and doesn't it end with them getting together? I thought the premise was you don't know u til the end