Corning Gorilla Glass DX

honestly, for me :
sport watch = screen protector ! 

GPS = screen protector

phone = sceen protector
etc 

basically everything with a screen, a lot cheaper than having sapphire and you can still scratch sapphire anyway.

I also use screen protectors on devices I want to sell after a few years. They are cheap and working brilliant. It doesn't matter if its Gorilla Glass, Gorilla Glass DX, Sapphire or something even more expensive: if you use an angle grinder and catch some sparks with the watch, it will burn in. Sad but true :-D

My question is does the screen protector have any negative effects that counteracts the DX features (reflection, contrast)?

Yes, almost always. Additional glass will always reduce contrast (because no glass is 100% transparent) and usually increase reflectivity. Additionally, most glass has higher reflectivity than DX.

I use a screen protector for my phone, and really I don't like it because especially outdoor the negative effects are evident.

I was hoping not to use a screen protector for the watch, but if I wear it 24/7 probably I will buy one.

Sapphire crystal is not so clear like Gorilla Glass, but I read it's very difficult to scratch. Corning Gorilla Glass DX+ should be clear like Corning Gorilla DX and resistant like sapphire crystal.

The other option is to take extra attention or to  wear the FR945 only for sport and change it after the activity with another watch.

Honestly can't tell the difference between before and after, what I can tell is that I scratched my 935 twice and my 945 once already and I'm happy I just have to peel it off and put a brand new back on instead of having a destroyed watch

Do you have a recommendation on screen protectors for the 945 - I read those for the 935 don't fit?

I put a 935 screen protector on that I had laying around and it is a wee bit too large, so it doesn't sit on the edges properly. I would have thought that if you find a reputable seller online and they sell one as suitable for a 945 it should fit (or you simply ask your money back).

Personally I always use one. It is a small insurance premium to pay to protect what is not a cheap device. I have never noticed any difference in how the screen looks.

I ordered this one yesterday.  I had to go back into my Amazon orders for the glass screen protector I had on my 935.  The company was called Exuun and I was very happy with it and wanted to get the same brand for my 945, but it seems the company is now called Poyoccit because when I click on that original order from 2 years ago this is the company it brings me to.  So I think it's the same.  We shall see.

https://www.amazon.com/gp/product/B07RX66XL1/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1