Guidelines required if an IDS(USG6625E) is configured before the Firewall device

Background:  I would like to configure USG6625E firewall to filter some unwanted attack. I have already activated threat protection license on the device.  I am using layer-2 in-line deployment and VLAN to separate the  2 ISP.  Both two pair interfaces are in an untrusted zone.  One security policy with default intrusion prevention “outside_firewall” profile enabled.

I have the following questions:

1. Are they any performance issues on this type setup? Should I enable hardware fast forwarding on this device? (note: daily traffic is around 100 gig)

2. From my past experience with TippingPoint IDS we should be able to have different filters set upstream and downstream traffic.  I would like to configure it as shown in the table below.     

 (Notes: Just one comment. I can not get huawei NIP 6xxx series device due import restriction in our area)

Please provide any guidelines on the above or best practice configurations.