Dear Rsuh,
The selection of the vendors depends on the materials. What is RFQ for? Then you need to go to the same supplier instead of going to any general trader.
For example, if you have a request for steel, please select multiple steel suppliers that are ISI and ISO standard. Then request for a quotation and select accordingly based on quality, price, and delivery period.
Please note that the highest-priced vendor is not always the winner. Select the lower-priced vendor, but ensure that the quality and delivery are acceptable.
Thanks,