In the past I have used Radio Mobile by VE2DBE to plot VHF coverage from various locations. It has been very interesting, but a little bit fiddly to use. You had to install the software, get terrain data from elsewhere and generally cope with a lot of settings. I had a look again at it yesterday, and was pleased to find that the author has added a web page version, and it is so much easier to use.
You can get plot of the likely coverage from any location worldwide, or look at the path loss between two locations. I have spent a happy hour looking at various summits, for example I hope to activate Sugar Loaf, Mynydd Troed & Mynydd Llangorse tomorrow, and it is interesting to see the different take off from each, especially Mynydd Llangorse, being well screened by higher hills. This is sort of backed up by the figures, with the 2M contacts from Mynydd Llangorse being only 29% of all contacts, whereas the Sugar Loaf has 54% 2M contacts. Perhaps better listen out for me on HF instead!
I have no connection with the author, but thought I would pass on what I think is an interesting tool.