Missing CSS rules

I’ve overridden the headings from ionics typography.css:

h1 {
  font-size: 2.6rem;

h2 {
  font-size: 2.4rem;

(and so on…)

but inspecting the element in chrome, reveals that another css rule wins, in my case:

.sc-ion-label-md-s h3 {
  font-size: 14px;

my fear is that there are many more rules I’ve to override. are they listed anywhere? I can’t find them in "~@ionic/angular/css/

another example where setting the font size does not work:

my css:
ion-item.ios { font-size: 1.7rem; }

opening the app in iOS Emulator reveals, that the font-size did not apply because the following rule is winning:
.ion-text-wrap.sc-ion-label-ios-h { font-size: 14px; }

how can I setup the font-sizes without ionic overwriting them back again? Any help will be appreciated.