should I use the ionic grid which is based on flexbox or use the css grid ?
use what better fits to your needs.
At the moment I can not give a better adive because my glass ball is busy with the new 2018 stuff that will come.
Happy new year and best regards, anna-liebt
PS: Maybe css grid with flexbox
If you use endless loading the ionic grid woud be the better choice.
The css grid reorders the items every time you load new items.