Clover Iron and crystal rhinestones
 

Do these get hot enough for placement of the hotfix crystals on quilts, don't want to buy the rhinestone heatfix tool if I don't have to. Also I am adding them to embroidered blocks is there something I have to place over them to protect the surface of my embroidered quilt block. Anyone with experience with this

I've done the crystals but I have the tool. Got it with a coupon at Hobby Lobby and it was only 6 dollars. It doesn't hurt the embroidery.

Did you get the plug in or the battery operated one at hobby lobby, there are 2 types

I've used my plug in one for years and it works great.

I have the tool, but why not just buy a small pack of the fusibles & just try with your clover? My gut reaction is that it will be hot enough.
You have asked a good question about using them on machine embroidery. ME thread is typically poly or rayon which is heat sensitive, however, there are lots and lots of patterns out there digitized specifically to add bling and I've never seen a warning about thread type, so I think you are good. Again if you are concerned, I'd just stitch out part or all of the design & see.

I put over 600 hot fix crystals on a quilt this year. I'm sure that the Clover iron gets hot enough, but the real issue would be that the crystals will probably slip around. The hot fix tool is dome shaped to hold the crystals in place as they adhere.

I think the iron will get hot enough to melt the glue on the crystals. But my concern is it may damage your threads or fabric. Some crystals take some time to get the glue melted. That is the purpose of the heat tool. The small 2mm and 3mm crystals would be easy with the iron but your larger stones 4mm and up may pose a bit of a problem. Also you will get problems with movement of the crystals while placing them.
Some crystals in the 4mm size have taken as long as 15 seconds for the glue to melt. imo you would be better off to purchase the heat gun. Personally I would get the plug in one so that I wouldn't have to worry about batteries.