Standard Motor Products has two grades of auto parts these days - a premium line, and an "economical" line for those looking to save $$. The premium line is typically backed by a 3 year warranty, but many of their ignition coils are now backed by a lifetime warranty. Their "economical" line, or T line are normally warranted for one year. The SMP premium ignition coil for your Envoy is a UF-414; the T line part number is UF414T. Standard Motor Products also sells parts under the BWD label. BWD parts also come in two tiers, premium and "economical". Their "economical" line part numbers end with a P suffix. The BWD parts are from what I have been able to tell are for all practical purposes identical to the equivalent SMP part (except perhaps for color).
Most auto parts lines these days offer two or three tiers of part quality. ACDelco for instance has the Advantage Line, the Professional line and the OEM line. The Advantage line is their least expensive parts line and is considered to be a "value" line aimed at people looking to getting their vehicle repaired for the least amount of money. The Professional line is a "standard quality" line of auto parts aimed at the mainstream auto repair. The OEM line is just that, actual OEM parts which are considered to be the best quality and the price of the part reflects that quality and those parts typically come with the best warranty.
By and large, cheap/inexpensive auto parts are just that, cheap, and they could be of questionable quality. Many times these "inexpensive" parts turn out to cost more in the long run because they fail prematurely and often there is little or no warranty on them. One part to never cheap out on is the fuel pump assembly unless you want to repeatedly drop the fuel tank to replace it. For a GM product, I'll only purchase an ACDelco fuel pump assembly or a Delphi fuel pump assembly. Delphi is an OEM supplier to GM and in many instances, an ACDelco fuel pump assembly is a relabeled Delphi fuel pump assembly.
I hope this has helped you. I know you only asked about what the non-T line SMP parts were, but I thought I would take the opportunity to share some of the knowledge I have obtained from the various automotive enthusiast forums I participate in.
Good luck!