Very quickly:
Kaspersky removed. One blink of a notice and then nothing. Still listed in Programs and Features. New one available for ten.
Okay, so do you clean up first? Big question, because getting the licence number from Barclays to give Kasper is a pain. So, I let Kasper install hoping it acted as an update. It did, and seems to have quite a few more modern features and mini screens showing data-flow etc.
So, I suggest, don't remove the old one first. There's only one showing in P&F.
CCleaner the same. It took ages to run first time. Given it's the one for 10 I HOPE they know what they're doing.
Setting FireFox as home page. That had me flummoxed until 03:00 this AM
It all worked, integrated it seemed, with 10. But, a darn notice kept appearing saying that FF was not set as main browser [Sic] Time and again I un-ticked the 'Show this' box but it just re-ticked itself and showed the warning box every time I called FF up.
I had to search the net to get that one sorted.
I went the old way - which gets you there. FF running, Tools, Options
SET the screen you want to start in (mine's just GoGo with the toolbars) Then there's a button to the right, Make FF your default etc. This takes you to a blue menu overlay which really had me flummoxed. Scroll down on the right side to . . . Aaaagh, it's of course not there anymore because mine's set, but I think Microsoft was mentioned in the button - anyway you can press them all with impunity, and this one shows a list of Browser Icons. I picked FF and it was done.
Now I use Snipping tool a lot. No real order to my life, so I just make a .jpg of receipts etc., and that serves well. Now no hint of Snip. I asked Cortana, and she found it for me in an instant. It still worked. Phew! Wouldn't want to be without that.