Setting Catalog - Performence

Hi!
i have few questions.

1. Ignore ACL rules (sitewide)  - we have guest, and registered users. Registered users sometimes have better prices, if i enable this setting this stop working, and all users was same prices?
2. Ignore discounts (sitewide) -
2.1 if i enable this, Client stop see discounts (old / new prices??
2.2 or if we enable this setting, discount coupon stop work in all places? and after add discount coupon nothing change? We use tier prices, discount coupon, and show old / new prices and some discount on products?   
3. Cache product prices  - if we use tier prices / and some products discount we shouldn't enable it?

Automatically detect language - if we have only one, we should enable it?

Well. Can't edit / remove post... so, for others:
https://www.nop-templates.com/performance-optimizations-in-nopcommerce-33