Never used it, but I can recommend you an app for lagging phones...if yours is a Samsung as I assume.
BK Manager is its name and can be bought for about €1-2 from the Google Play Store. You have the option to disable all bloatware that Samsung installed on its smartphones or simply go through apps manually and disable what you don't need anymore or any service you simply don't use.
It's very easy to handle it and on my Galaxy S7 works perfect. You might get some more juice from your battery by using it also.
OK, thanks for good info @acesontop. Does it requires rooting the phone?
Been trying various boosters, cleaners etc - most seem to be eventually bringing more bad than a good...those popup adds, etc etc
No it doesn't. I never used any booster ever since started using using BK Manager. They are just power hogs. If you have any questions after installing it feel free to address them.
For a better battery life I only use app power monitor that is Samsung's own way of saving some juice, but you won't see too much difference. Using black themes or wallpapers will help though.