I emblemed a couple 4* that I then reset for their 5* equivalent once I had it; Grimm was emblemed and very helpful until replaced by Athena, Triton was emblemed and awesome until replaced by Magni.
Some other 4s will keep their emblems: Wilbur+18 is life on titans, Jackal+15 for obvious reasons, Falcon only +4 which is sufficient (he shares with Frida), Caedmon+10 is a necessity for me and fantastic in his role. BT+7 might actually get stripped one day but not now. Sabina+11 is only for war and my least favorite but no other interesting sorcerers.
I have been playing a looong time and while I am C2P, my roster has built up nicely. I emblem 4* to fill in gaps in my 5* and to deal with titans. I decided to put the emphasis on my war defense team first, then second priority was titans, so Jackel and Falcon for their specific color defense down, and Wu because I don’t have Ranvir. Not going with Wilbur yet because his emblems are going to Joon. I am starting Sonya because I want a 5* blue debuffer. I don’t have a 5* blue healer and would do Kiril, but his emblems are going to Hel.
For 4* you can make them an equivalent to a 5* if you max emblem them. E.g. Grimm becomes comparable to Isarnia but better mana speed when Grimm is max emblems.