I can tell you what I used and maybe that can help. Ok,so the lakes I used a modified X5. That has been my lake machine for 15 years. They weren't made for water hunting but really anything can be converted. I line the scoop with mesh wire so no smalls fall through. Then dump the sand into a floating sifter. I will say most of the silver and gold came from outside the main swimming area.
For the wet sand hunts I used the Minelab SE pro. I have used the Explorer line since 2001 and am just comfortable with these. I do know I am missing smalls in the wet sand for sure. I grid with my digger. I don't snake or wander down the beach. I look for slopes or black sand and just grid line that entire area. If the whole beach looks like that I hunt as much as I can. If the beach is flat or mushy I skip over these areas.
The dry sand is a new unit for me. I picked up a Tesoro Mojave on the forum a few weeks ago. Paid $200 and it was pretty much new. Best cheapest heavy trash detector I have ever used!!! Now I don't run down and hunt around the lifeguard stands! I'm not saying they don't produce. I'm saying everybody runs there first so I hunt in the back of the beach,along dunes,near gas lines and drain pipes. Where other machines will pick up the whole pipe I pick out the targets above them. This machine is not deep by any means 6-8" is about max with the 7" coil. It's not shabby but it ain't a Minelab or Fisher. It has its application and one has to know where it shines.
Donna here has a Deus and I think the high frequency coil sounds awesome for small jewelry. I have no experience with this detector.
The impact sounds cool. I like the 99 tone thing If I heard correctly. Could be a great dry sand,park,school machine. Doubt if will beat a Multi-frequency machine in wet salt. I think the impact has multiple frequencies but only can operate at one at a time depending on what is selected. I could be wrong on this. I do like Nokta. I have an Au Goldfinder that has found a lot of gold over the last year. That is at lakes and schools. Dry sand beach it may be good too but have not used it there. I doubt a high frequency machine would be good in wet sand. I would not recommend this if you don't like trash. You can eliminate iron but it has low discrimination like most gold machines. If you like digging tons of trash to pull a few gold then it is awesome!!!
That may or may not help but that is what I hunt with and some tips. HH,Harry