I haven't used it in a while but I did use Gaia GPS
https://www.gaiagps.com/ I can't remember exactly how the purchase went, I think you bought the app and then there was an add on subscription if you wanted to get a whole variety of maps to make layers. I liked it but I never tried 250 pins, more like one or two pins and a bunch of tracks. Looking at my phone I see I am a GaiaPro subscriber so I don't have to buy the new version so I'll try that but in the meantime I opened it up to refresh my memory and I see I have 12 layers of maps to pick from immediately and there are a lot more available. I think I pretty much used Open Hiking, USGS Topo, Gaia Topo, US Shaded Relief and when I was visiting NZ New Zealand Topo. I also have VFR Sectionals and NOAA Charts. I bet a fishing BBS would be a good place to ask about ease of pinning locations, that or maybe a Geocaching forum.
Its funny I use two GPS apps for my boat INavX and Navionics Boating but for some reason I don't use the Gaia.
I believe Navionics does a hiking app but I have no familiarity with it.
The one thing that is important if you need it is whether or not the app you pick will work offline. All the ones I have mentioned work with no internet connection, Gaia had power conserving tips and the only downside I remember about it was that sometimes when you downloaded a section of map sometimes there would be a glitch at some zooms because a map tile for that specific magnification wasn't loaded right or something.
The Navionics seems to work pretty good for the boat, any problems it gives I think are down to the fact I have it running on an Ipad 2.
I like INavX but I believe it is purely for the water, also it is a little unfriendly in bouncing you out a global selection of charts and you kind of have to remember what chart you are on.
They like to suck the battery dry.
If I have time I'll see what putting a bunch of pins into Gaia is like.
If you have cell data service than probably google maps would be pretty good, depends on where you are going and how much information you need on the map.