Questions for mobile optimization

Hi, I am currently working on a mobile game, but the optimization problem made me do things all over again.
(I’m mentally exhausted.)
This is because most mobile devices can’t run the game. So, I had to post questions regarding my problems.

 When I type "stat rhi" on the console, I see that I have about 300 statprimitive drawcalls, but I this is actually a blank map with only a landscape. I would like to know the proper "statprimitive draw calls" for most devices these days.

Q1: What is the proper number of statprimitive drawcalls, in regard to fitting into the capacity of average mobile devices these days?

 Also, I created a small landscape with minimum number of components: 7x7 Quads, 1x1 Components. 200x200 in size. I am using three 1024 textures for the landscape material. Even this causes texture streaming pool over 6mb, hence I made the console command, "r.streaming.poosize 1000" but is this a proper measure?

Q2: Did I create good landscape for mobile devices? Will the change of streaming pool size matter?

 Perhaps the most important question; I am managing "Trangles Drawn" around 100,000 in mobile preview. Furthermore, I made resolution settings so as to boost the performance of devices to cope with 100,000 trangles.

Q3: “trangles drawn” to 100,000 is doable?

 I am turning on "Mobile HDR" and how heavy is this affecting the game? Could you give me an example?

To sum up, I had to re-do level design all over again for about 4~5 times, as LG V30+ keep on showing its default screen instead of loading my game even it is considerably a high end mobile device, and searched documents for optimization. But still I can’t get the picture of how much should I squash these. The least mobile capacity I am thinking for my game is “Galaxy Note 4” for android, and “iphone 6” for Apple. This game is a third person RPG by the way. Thank you for reading.

A1: I’d recommend below 200. Aim for least possible though.
A2: I’d go for least components possible. If it is 3 textures in total, that is totally fine. If you have 3 textures per layer and a dozen of layers, that is bad.
A3: Should be doable.

I double checked on mobile preview, and it is about 180 drawcalls. This means iv done everthing pretty well, but still i cant load the app, it just shuts down. Is there any other factor that u suspect?