Dell Venue 8 Pro 5830 Vs. VP8 5855 - Clean Win10 Performance

Hi there, I've got a question: I own both of the tablets stated above. I have the model VP8 5830 with 64GB/2GB RAM/3G-Modem and the VP8 5855 with 64GB/4GB RAM/ WiFi only When I got the VP8 5830 it had Windows 8.1 installed originally. When there was possibility to upgrade to Win10 Pro for free (from M$) I made the upgrade and gave the 5830 a 'fresh' install. Over time I realized the 5830 didn't suit to my preferences any more, because it was a lil' bit 'laggy' or 'slow' in different occasions. So I bought a Model 5855. After that I became a father, so had not really time to do the migration, and keeped with the 'old' 5830. Some weeks ago I finally managed to do the migration and changed to the 5855 with a freshly updated Win10 Pro. But, sadly, I had to realize that this 'new' Model seems to be pretty slow also. It seems even slower than the old one. Even just for scrolling websites, clicking around on the Win10 menus or just browsing the storage it needs it's 'moments of thoughts' (lagging a bit). I'm asking myself if this just normal? I can't believe that Win10 pro runs smoother on the old one with half the RAM!? Could it be the reason that I'm using the pre-installed Win10-Pro? Did anyone do a 'Clean-Install' of Win10Pro and had a remarkable difference in terms of (overall) speed/usage? I'm a bit frustrated since I love the 8" form factor and it seems there are not really more 'modern' devices on the market. But perhaps the change to a 'clean' install would help....? Thanks for any suggestions Best regards, Frank