Hello, i am using logseq both in my phone and pc
I use logseq app on my android to capture notes. My question is : its better to use one page to put all notes with their tags (so i don’t need to enter to this page because i found the info in the references of tagged pages, which make logseq the best 
) or to use the journal (which i am afraid to use it because of creating a lot of journal page.md which can slow down the app.)
And thanks
I use journal block entries, adding the corresponding block property layer to each one. (see below). This way you keep a time-related way of tracking them, a very valuable context to retrieve them out, besides the metadata you attach to each entry.
Have you experienced the app running significantly slower using multiple pages vs 1 page? I have lots of pages and my phone is almost 5 years old.
I am just wondering before creating hundred of journal log pages
Having so many entries to make hundreds of journal pages would also mean having enough content to make one really slow page.
The app can lazy load journal pages.
Just use the journal to start recording notes. Worry about the maintenance and speed in a year or two.
Tldr? Just start taking notes now.