I have a Lenovo H50-50 with i-4460(84W), 8GB DDR3, factory installed GTX 745 with factory installed 280W PSU. When I run GPU-Z with this configuration, in the "advanced" tab there are no "Board Power Limit". When I install a MSI RX 460 4GB(tdp:75W), the advanced tab reads Board Power Limit: 48W. I tested the RX460 and even if seems to run at 100 for half an hour, it does not seem to draw beyond 50W. How can I be sure it is limited by the PSU? Online power supply calculators are usually give BS results, like Cooler-Master's calculator page telling me I need 320W with factory configuration, which means Lenovo factory installed an insufficient PSU! This here https://in.msi.com/power-supply-calculator and this https://www.bequiet.com/en/psucalculator gives much lower requirements.
I suspected that GPU-Z shows BS numbers and run it in a gaming computer with a Gigabyte-something high-spec mother board, 500W PSU, i7-4790, 16GB DDR and R7 240. It read "Board power limit: 42W" Now, that I cannot take seriously. TDP of this card is 30W and all the internet says PCI-E limit is 75W.
Whom do I believe and how to be sure if my PSU can feed RX 460?
I'm sick and tired of all PC and component manufacturers not giving sufficient specs and answers. Once again I have to ask a lengthy question in this forum. I think manufacturers should give money to forums. Thanks in advance. Sorry if this should be on software section.