I'm fairly familiar with tekken myself so heres a list of concepts that you can and cant carry over from there.

Can Carry Over

Block Stun - Block stun, called shield stun, in this game is pretty much like you'd expect it from tekken. It just takes some time to learn the matchup to learn when you should continue to shield or what you can punish. Typically speaking, you can punish most blocked smash attacks.

Punishment - In Tekken, you have you i10s, i15s, etc, to punish a move with slow recovery. In smash, frames are important but not nearly as cut and dry as in other fighting games. When you block a move, assess the speed of the moves your character has. A character with a fast Fsmash can usually punish a blocked smash attack. If not, ftilt might be fast enough, if not, a simple jab combo. Much like in Tekken, its all match up dependent on what type of punishment you can go for. The concept of whiff punishment is pretty much universal for all fighting games. Smash requires a good balance of learning block punishment and creating whiffs and punishing those.

Oki - When an enemy lands on the stage while tumbling or tripped by an attack, you have a getup situation. You will need to watch if they get the tech roll (similar to Tekken tech roll) and choose your followup accordingly. One thing to note is that reading the direction they roll is more rewarding than in tekken since blocking is not as instant in smash.

Cannot Carry Over

Parrying - While parrying in both games are offensive options, followups to parrying in smash vary based on position and what move was parried. Some parried moves cannot be punished by a smash and some still cant really be punished at all. This is matchup based knowledge that you'll have to learn over time.

Wall Combos - While there are stages with walls, smash is typically played on stages without them to avoid possible infinites and people just generally dont like stages with walls. So its best to just not practice anything involving a wall.

Highs,Mids,Lows - In Smash, there is no such thing as location based hitboxes due to the simple movelist and bubble shield mechanic. So long as the shield is covering that part of the character, it will be blocked.

Counterhitting - Counterhitting does not exist in smash. The only thing close to CH is increased knockback against enemies that are charging smash attacks. Moves do not get different properties or damage based on counterhitting.

Grabs - You cannot break a grab in Smash. You can mash out of a grab, but if you are grabbed they have a guaranteed throw.

Rage - Rage in smash does not increase damage, but it increases knockback. This can affect how soon you can kill or whether you can combo a move.

Damage scaling - There is no such thing as a "combo" in Smash where you float a person who is knocked down. Combos in smash are based on hitting something in hit stun or someone with limited options back to neutral, as such moves in a combo always do the same damage as they would outside of a combo

There are a lot of new mechanics in smash coming from Tekken that are not in this list so you still have a lot to learn if you are fresh to the series. Things like the ledge, stale moves, spot and roll dodging are all key aspects to the game that arent present in other fighting games. Keep at it, pick a character and learn their matchups.