My opinion for what it is worth which isn't much really
Information comes from the strangest sources, so follow them all but be prepared to share. I keep a little tree on GR and don't pay subs. I get contacts and once we establish we have a real link I offer to open my Ancestry tree (pics certs the lot) if the person is forthcoming and willing to go with it and share. If I know it is a positive link once I fish about a bit but I don't feel the good vibrations I let them view my little GR tree, because I don't believe it is worth being mean (even though I have spent a flipping fortune), if I can help.
Sometimes you have to cast your brancehs wide, as someone may just have that illusive info or pic you do not, or you may have their Aunt fanny sitting on a wedding pic at your G Aunty Flos' reception, some of my best swaps have been with distant twigs.
What I do find though is a lot of people on GR willing to open their tree and have done so on the initial PM, very trusting of them so it is.
I have been blessed with some fantastic contacts, and hope I have been equaly good for them.
I have pics of nearly all my G Grandparents now and one GG, thanks to contacts.
Be cautious be helpful but also be understanding, not everyone knows how to go about the building of a tree. One lady lately took about 2 months to convince she was not related even after I showed certs and all sorts to prove it, but bless her when she finaly admitted she was wrong and needed to start again she said "I think I just so wanted to have your tree family as mine they look so lovely"
I so wish I could have obliged