Help me setup this network

I have to upgrade a medium sized school campus network, which contain around 1500 users and 70 access points.

We use 6 Cisco 2960 as access switches and one 3850 as core switch, which is all connected in a daisy chain manner,

I was planning to stack the current 2960 switches and connect each stack to core switches which is 2 Cisco 3850 Switches.

If i do this kind of setup , will it cause a data bottleneck

I am also planning to setup byod, where i need only basic setup.

I first considered Cisco ISE, but later thought it will be way more expensive and should use cisco ASA or fortinet to do the basic Byod Setup.

Can you guys advise me on this setup , how should i move forward with this.

How should i connect the core and access switches, can i use 4 stacks with each stack containing 2 switches , connecting to a stackehd 3850 core.

Should i go with fortinet or asa for Byod?

I need your help, i am new to all this.