Hello @yabapmatt vests are basically Steem Power held in a fund. Vests are Shares in that fund. Here is an example if you had 1M VESTS today it would be worth $699.28 which would be = to 482.26 Steem Power , the price of Steem changes the vests value all the time example 482.26 Steem * $1.45 (7 day avg Steem price ) = 699.26 . This is about all I can tell you about the vests.
Now about the slider for up voting you do not have enough Steem Power to have a slider yet. When you reach 500 Steem Power you will get the slider automatically so I have been told .
I hope this helps and happy Steaming