yes Me too experiencing the same issue of a total lag, and unfixable. I say unfixable in the moment, because i have and continually do what the recommendations say (delete cache, delete cookies and data, delete history etc). I even have a blank page and no preload top hits as start page, because that was causing a lot of problems.
Also, i can't seem top be able to click on the url earch bar and type + press enter/return for a search to execute, because as soon as i have typed my search word, Safari selects the whole search term in gray, and blocks the return/enter button from being a command to 'go search'

I then have to click a second time on the url bar to unselect the blue texted word and press enter again to search, because the first press of the enter button doesnt work.
And the reaction to search after i click enter for the second time, is as you say, very slow indeed.
I notice startup of Safari is also very slow (and im talking about no histtory no cache, no cookies and no top hits or homnepage,, bare bones! and its still slow as heck even with an i7 CPU and 16gb RAM!!!)
I have a Macbook Air and an iMac 27 also the same on all devices
One thing that did speed it up a bit was removing all safari icloud tabs between devices, and setting the mac to not use icloud notes etc
iCloud notes and mail turned out to be one of the main reasons my Mac has been so slow lately. Since i reset my Mac without my apple id and icloud connect, it workds fine except Safari, which is still slow, and also startup, which now takes 5 times as long as a windows device to load the desktop and menubar. I remember the Apple adverts showing how fast a Mac starts up compared to a windows device, but now the advert is laughable, considering the opposite is now true
The Mac is the slowest device in the world to start up and load desktop since Yosemite came along, and El Capitan has made it worse. I did have Sierra installed when it first came out but i downgraged after half a day, because i found i9t terrible. All the things i wanted had not been incorporated, and all the things i dont want, have been (for example i dont want a permanent facebook account add option - a Mac should not have a permanenly built in Facebook Profile Add option, or am 'add twitter account' or 'add Flickr account' etc. Such should be downloadable, but not permanently built into the accounts settings).