Well you don’t technically have to use Bootstrap. The thing to keep in mind is a big part of Bootstrap is streamlining the css styling you have to do, not negating it. Meaning you can do everything stylistically that you get with Bootstrap with just plain old css.
Being a framework, Bootstrap speeds up production time because of all the built-in stuff. But you can totally make that entire template you linked with just html/css. But it would take longer to do it all from scratch. Which is one of the pluses of using a framework cause it takes out a lot of the guessing and trial and error of putting together a layout that functions/responds perfectly.
If you’re looking to hone your html/css skills, I’d say try making the site with just those, no framework. Get as far as you can with it. And afterwords try building it again but this time using Bootstrap.
As for tips, check out this massive FCC Bootstrap 4 guide: https://medium.freecodecamp.org/bootstrap-4-everything-you-need-to-know-c750991f6784
I haven’t gone through it myself yet (learning Bootstrap is on my agenda in the new year), but it looks really thorough.
And if you’re looking for some good old fashioned responsive css methods check out: http://alistapart.com/article/responsive-web-design