For the old Puzzle Board that's used on the show from 1974-1997, they slide in the letters & characters in that's used for each Round's Puzzle.

Since it contains 3 sides, considering its a Trilon-Based Puzzle Board:
There's a Green space
an Blank Active/Inactive side
and an occupied side containing the desired Letter/Character that's used for that Puzzle in each Round.

The Current Puzzle Board that's being used on the Television show is an Electronic one which was started in 1997 & still going strong to this day.
The First Design of the Electronic Puzzle Board was a Golden Boarder one which was used from 1997 to 2003. By 2003, they switched to an LED Boarder but the Electronic Puzzle Board remained the same.

As for the Gameplay Elements in that show. Here's some of them & when they lasted:
Showcase Shopping = 1973 to 1987 (Nighttime) & 1989 (Daytime)
Half Car = 2011 to 2019
$10,000 Wedge = 1994 to 2008 (In 2008, the $10,000 Wedge became the Million Dollar Wedge & Bonus Envelope)
Double Play = 1995 to 1996
Free Spin = 1973 to 2009 (Wedge Mode: 1973 to 1989 & Token Mode: 1989 to 2009) (In 2009, the Free Spin Wedge and Token became the Free Play Wedge)
Jackpot = 1986 to 1988 (Daytime) & 1996 to 2013 (Nighttime)
Surprise Wedge = 1992 to 1998
$1,000 Cash Wedge for Round 1 = 1983/1987 to 2000
Clue Puzzles = 1990 to 2008 (NOTE: These include Fill In the Blanks and so on, with a Bonus Cash Prize ranging from $250 in Daytime or $500 in Nighttime from $1,000 to $3,000)
$500 Mystery Round = 2002 to 2005
Prize Wedge = 1989 to 1991 (Daytime) & 1983 to Present (Nighttime)

As for the Bonus Elements:
5 & 1 Vowel = 1981 to 1988
WHEEL Envelopes = 1989 to 2001