WiFi Performance of JR6150/AC750

Your provider may be trying to upsell you a "better" router that they will charge rent for. It probably won't be any faster.

The Wi-Fi speeds listed in the specs are link speeds. Real world speeds are much less, typically at least 50% less. In fact, at 2.4 GHz, a link speed of 300 Mbps is not possible when neighboring Wi-Fi networks are active. Wi-Fi standards require that link speeds drop to 150 Mbps to allow fair sharing of radio spectrum. Technically, the standards require the use of 20 MHz channels instead of 40 MHz. You can a maximum real world speed of 60 to 70 Mbps at 2.4 GHz at close distances.

The situation is better at 5 GHz. There are much fewer 5 GHz networks deployed, channel widths are higher (40 MHz and even 80 MHz options are possible), and the protocols are better (802.11ac is only available at 5 GHz). As a consequence, real world speeds will be much better. A 802.11n client running at 5 GHz should be able to link at 300 Mbps at close distances, with a corresponding throughput of 120 to 130 Mbps. A 802.11ac client can probably break 200 Mbps on a JR6150. Of course, your Internet service is capped at 100 Mbps, but data transfers between devices at home will be unrestricted.

The real world numbers I have given are best case. They will drop as distances increase and as environmental factors intrude, such as walls and radio generators such as cordless phones and microwave ovens. Speeds will also depend on the capabilities of the devices, too. They may not support 5 GHz or 802.11ac. In other words, actual speeds may vary.