Hi
I am new to ui/ux design. I have 20 years of magazine design behind me and now I’m venturing into the app world. Mostly to create news apps.
Every respected newspaper or magazine in the world has its design streamlined over all channels. Print, web, mobile.
I am working on my first app for a magazine I redesigned in the media house I work for. So, of course, I want my magazine style to translate to web and mobile.
So, I have several questions regarding font usage.
In the magazine, I am using only 2 fonts. Serif and sans. Everything standard, but in several weights. Normal, bold, black, cursive… etc…
I know that including all of them on the web page would slow it down! So I know I will have to limit myself to using only 2 weights of each.
But how about the apps? How are apps dealing with fonts? Are they included in final delivery to the developer or are they downloaded from some cloud when users open an app? Something like Google fons!?
I wanna retain my design style but also don’t wanna jeopardize usability.
Any info regarding this matter is thankful.
BTW I am using Adobe XD for app and web design.
You and I seem to have similar backgrounds in publication design (that extend beyond baseline grid issues). 
I’ve also faced the same set of problems in juggling publications with their digital equivalents. I think it’s important to embrace the fact that digital and print are different animals that (ideally) need to be approached separately.
Of course it’s important to establish visual tie-ins between, say, a printed magazine and it’s online version, but it shouldn’t be done in a way that compromises the effectiveness, readability or possibilities of one to accommodate the limitations of the other.
Both digital and print have their advantages and drawbacks, so it’s really important, in my opinion, to not think of the digital version as needing to mirror the print product. I’ve found that it works better to think of the digital product as being its own thing that shares content and personality (to a degree) with its print sibling.
For example… Typefaces that work great in print, do not necessarily work well on smartphones. Websites or apps have no equivalent to a two-page magazine spread. Since they need to work on everything from large monitors to smartphone displays, websites shouldn’t really have fixed layouts and should, instead, reconfigure themselves to match the devices on which they’re being read. Non-system fonts, as you mentioned, can be automatically downloaded for websites, but they’re typically embedded into a stand-alone app. Print has space limitations whereas stories are written, edited and trimmed to fit. Digital does not have this problem. Periodicals have regular print dates and deadlines — online publications can be updated as often as needed.
Anyway, what I’m really saying is that as important as visually tying the print and digital versions together might be, it’s more important to avoid needlessly compromising one for the sake of the other. Make them visually match to a degree, but realize, accept and take advantage of their differences. Of course, practical things (like money, resources, staff, etc.) limit what can be done, but it’s important to not lock the digital versions (web or app) into formats that are too tightly tied to their print sibling. Otherwise, you’ll be facing a fundamental digital redesign a year or two down the road when the problems related to their innate differences become more obvious.