.
Unifi Air 4G LTE modem plans use TM 4G LTE network which has poor coverage while Unifi Mobile Bebas phone plans use both TM and Celcom 4G LTE networks since Feb 2019. Celcom has much better 4G LTE coverage. .......
https://www.nperf.com/en/map/MY/1735161.Kua...1.68653&zoom=13

A 4G cell tower has a range of up to 3 miles/5km for Internet data and 10 miles for voice calls/SMS. 4G cell towers are usually located in city areas and along main roads and highways(= to cater for car nav apps like Waze). 4G cell signals are line-of-sight = blocked by walls, tall buildings, hills, etc. A 4G cell tower can only serve up to 60 users at any one time, on a 1st-come-1st-serve basis = network congestion during peak hours will result in slower dl speed and inability to connect to the network.

TM Unifi Fiber and Unifi Air are truly data-unlimited because TM has a monopoly on the HSBB Fiber network in West Malaysia. Even all its Unifi Mobile phone plans are data-unlimited, except for the postpaid UM 59 phone plan which is data-limited to 12GB per month. So, expect no throttling by TM unless TM has detected you doing P2P/torrenting or breaking the AUP, eg use the Unifi Air 4G modem plan on a 4G phone by transferring the SIM card.

3G HSPA = about 1.5Mbps
4G LTE = about 30Mbps in download speed.
4G LTE-Advance = about 130Mbps = Digi has just upgraded to this.