The strongest dilution I'm aware of that pre-set inline sprayers give is 1:8 which is probably too weak for any protector products that you need to dilute to use. I know some variable ones supposedly go down to 1:1 but they aren't accurate at all, the system is very crude
There are two other problems which mean you couldn't use them for protector. Firstly the flow rate would be way too high, you need to be pumping a fair old amount through it to actually get the venturi system to work properly. Standard jet size is '08 and any lower compromises the venturi, you get back-flow into the container and it'll actually fill up rather than empty!
Secondly the dilution isn't 100% constant so it's a bit of a ham-fisted way to apply a product that needs accurate application. You' end up drastically over-wetting and/or over applying the product
I'd stick to a standard sprayer or at the most an electric one.