As you'd expect Titleist make some of the best fairway woods in the game and as a result are used by some of the best players in the world. Justin Thomas, Jordan Spieth, and Adam Scott have all used Titleist fairway woods to help them life multiple Major championships. In a nod to their quality, on the European Tour, Matt Fitzpatrick (who can choose to play any clubs he likes as he is non-contracted) still has (in 2019) a 917F2 in the bag, first released in 2016.
If you look further back into the history of Titleist fairway woods, you'll see there is a constant evolution in shape and design, rather than a total overhaul which you might see from other brands. The journey from The PT 906 fairways to the TS family of recent years (launched in 2018) is clear to see - in part, thanks to Titleist's regimented launch cycle of two years. The only difference being updated technology, which follows the pattern set out by their driver line up.
Most recently this technology was in the form of the Titleist Speed Project. As the name suggests, the focus was clubhead speed with an ultra-thin titanium crown, thinner and faster face, and a new streamlined shape all designed to increase ball speed without having to increase input. Within the TS fairway family, there are two models. The TS2 is set up for maximum forgiveness with a visible weight low and back for optimal CG, high MOI, and high launch. The TS3 features Titleist SureFit CG for the player who wants to set their fairway wood up for a preferred and repeatable shot shape. Titleist SureFit CG was first introduced in the 917 fairway wood.
In addition to CG adjustability, Titleist also has their SureFit Hosel system. The dual cog system allows for loft and lie to be adjusted independently from one another to deliver 16 different settings to create the optimal launch conditions.
Before the use of a number to differentiate the different models, Titleist used 'F' and 'Fd' up to and including the 915 fairway wood. The 'F' was the standard model (compare to the more recent models with '2' in the name) and featured a larger footprint for maximum forgiveness and easy launch. The 'Fd' models (compare to the more recent models with '3' in the name) are slightly smaller and deeper faced with a more forward CG location which will reduce spin and create a penetrating flight - both characteristics preferred by the better player.
Whichever model of second-hand Titleist fairway wood you go for it will still be extremely playable, of outstanding quality, and unconditionally identifiable as Titleist.