Ex6100v2 AP Performing Worse Than Extender Mode: Why?

I decided to switch my EX6100v2 as an AP instead of an extender. I have an AC1750 Wireless Dual Band Gigabit Router with 400 down. The EX6100v2 extender was consistently okay, but sometimes it will drop and show high Dbm. The signal strength is normally at 117 Mbps with 2.4 ghz. I used the smart connect and one wifi name.

After 10 days of isolating in a different room made me realize these poor results. So I wanted better performance and bought a Cat6 100ft (more than needed) to setup the AP. I thought it was plug n play set up through the web client.

I enabled 2.4ghz and 5ghz. I expected better results but both settings output slower performance than the extender settings. First, I wanted to share one 2.4ghz name and 5ghz name then created separate names after spotty connection issues. After connecting to both, the speeds weren't even close to the 400 Mbps. The 2.4ghz was very slow, dropping, and showing Kbps. I was able to connect to the 5ghz, but poor speeds and buffering. I checked the network properties on my laptop to see link speeds. Both link speeds were at the AP's speeds: 300/300 and 433/433.

Why is this happening? How can I resolve this issue?