Install stone benchtop and waterfall

im going to install for the first time and engineered quartz stone.

I live in remote area and is only two stone mason, one don’t wanna donthe job because I didn’t buy the stone from him and the other one want 2000$ just for install a3 piece benchtop what is ready in my home.( is totally over my budget, I was expecting around 400$)

My only option is doing myself.

I saw lot of video and I know what I have to do, but I’m not sure about what kind of product use.

About the joint I would use tenax looks like lot of food reviews. ( the stone is white should be not to hard to make invisible joint or atleast not bad)

About the under benchtop I read about normal silicon, is any silicon better what donthe job better then other for this job?

The most important question is about what kind of glue is the best for anchor the waterfall to the cabinet?
In all videos I see everyone use some caulking glue , what is the best strongest glue? The ideal glue between waterfall and cabinet for make sure the waterfall will never fall and injury someone .

Thanks for anyone can help me about choosing the right components.