I can't be sure without hearing exactly what you were told, but I suspect you are getting bits and pieces of different suggestions that may not exactly go together with YOUR gun and selected bullet.
What you need is a coherent loading that becomes an integral part of an efficient shooting system. I'll try to explain.
First, Bullet Weight:
Although it is possible to make major with 155gr in .40S&W, most USPSA competitors I know, including me, use 180gr. I use Precision Delta Jacketed TC over a near-max load of HP38. Remember. power factor is bullet weight times speed, and it is easier to use a heavier bullet than load to MACH 2.
Second, Loading Data: You will find a lot of proven load data specifically for competition on the Brian Enos forums. There is no need to reinvent the wheel.
Third, Seating depth: Some specific barrels, such as the competition models from STI and SVI, have longer barrel throats and open chambers for better reliability when running fast, hot, and dirty. Many shooters feel it is better to load the bullets longer than SAAMI standard to offset the longer throats and get better accuracy and feed reliability. At any rate, cartridges loaded long for these competition barrels will surely cause jams in barrels with SAAMI standard dimensions.
As the seating depth of a bullet is changed, adjustments are needed to keep the velocity at required Power Factor. In general, the longer out you seat, the lower the pressure and velocity you get.
Finally, Recoil Spring: The recoil spring needs to be matched to the competition load you select. Too strong a spring makes the gun sluggish and can cause feed failures. Too light a spring makes the gun very quick and snappy but batters the life out of it. I saw one race gun slide separate just behind the port and eject the back half of the slide into the shooters lower teeth. Keep a spare recoil spring in your range bag. (I like ISMI for the 1911 platforms).
Once your load is selected and your gun tuned for it, load up a few thousand and try to wear out the gun in the next few years.
Good shooting!