Any comments or questions on the attachment? So far it's all digital except the tubes and manifold; they are in place.

you're preheating your cold in? why both a tank and a tankless? We haven't had much luck with flow switches, but if you need one, it needs to be downstream of the mixing valve, you might not get the flow you need on the side of the mixing valve that can see possible restriction.
I would consider a cheap reset control like a 356 to run the pump on the water side of the HE at variable speed.

Yes I’m preheating all of the water. The efficiency of the drain water heat recovery is higher with more flow, (more heat gets extracted) and there is opportunity to recover the latent heat during cold water use. Besides how often do you need 2 degree, (35F) cold water? Our drinking water is in the fridge so it’s unaffected and with the water not as painfully cold there is less pipe and toilette tank sweat, less hot water demand for washing etc.

The tank in combination with tank-less is due to a couple of factors; first being heating capacity. I can’t get enough electrical service to my utility room from my panel to drive the radiant system with a tank-less on its own. I also have the thought of adding solar assist or a fuel source for the hot water and the tank gives a little more future friendly flexibility. For now I will “steal” heating capacity from the DHW when needed for the radiant system, (coldest days of winter only) but also have the tank-less in place to serve endless hot water, (within limits) for the domestic requirements. It seems like a happy, (but slightly more expensive) middle ground.

Thank you for the flow switch location warning. That makes perfect sense and was overlooked as the drawing went through revisions. I will plan on it downstream of the mixing valve.

I will start thinking about speed control on the pump. It could prove to be a worthwhile addition to the system.

I was going to say the same thing about running the entire house cold supply through the DWHR. Our kitchen cold is bypassed on this but bathrooms are not. In my opinion you’re better off running all the cold through rather than none of the cold. Our local inspector would not let us plumb the cold through the recovery unit. So I had to change it after the fact, they sited some clause about potable water running past wastewater, ignoring it is double walled and the potable water is under pressure and the wastewater isn't... Go figure. Anyway my wife did notice a difference in the bathrooms brushing teeth and such, but having the cold water 15F warmer helps out a LOT on the shower side of things. Personally I noticed a tiny bit of pressure loss when running two showers at once even though the recovery unit was not suppose to drop pressure more than 5 psi maybe that is what I was noticing, it is ¾ in and out.