I think the choices made in the series (for Part 1) were perfect for what they needed to be for the narrative. The only one that should've been changed is Goku VS Panputto being swapped with his match against Chappa. King Chappa was an opponent where Goku displayed far more skill and growth against, so having Jackie Chun use Panputto as a benchmark for how much Goku had grown into the superhuman level was completely off when defeating Chappa was infinitely more impressive.
For the 25th TB, I'd have definitely made Piccolo VS Shin more than a staring contest, even have Piccolo defeat Shin before learning who he is like he did in the BT2 What-If Destined Rivals. Him just submitting to someone just because they're above him in the God hierarchy shows how much Piccolo's integrity had fallen after fusing with Kami and was the start of his character's fall from grace.
As far as alternate scenarios that would change the story significantly, I doubt anything major would change from the 21st TB if Goku lost to Giran or Namu when he'd still gain the lessons from Roshi about there always being someone stronger and having his tail never affected his journey much when he didn't seem to travel at night. It'd mean Jackie Chun doesn't fight Man-Wolf in the 22nd TB, but that's about it.
Having Chaozu defeat Kuririn in the 21st TB might change things depending how Goku goes about things. It wouldn't change much if he uses his full speed to easily beat Chaozu from the start, though getting trapped by his telekinesis and beaten would drastically change Tenshinhan's character arc with him still remaining with Tsuru Sennin (albeit, conflicted about his path). With him not showing up at King Castle, Goku has an easier time beating Daimao as he's not hindered by Piccolo taking Ten hostage. At the 23rd TB, he loses to Tao Pai Pai in the quarter finals and finally has his redemption upon seeing the power progression of the Turtle School fighters. Not much changes after that though.
The only 23rd TB match which I think would've heavily affected the plot is if Kami successfully sealed Piccolo. Without Piccolo around in the Saiyan Arc, things are far different against Raditz. Even if Goku gets the help of all available fighters, he'd still end up letting go of Raditz's tail and even if things play out to the full nelson, I doubt a combined attack from the Earthlings would kill Raditz. Assuming it does though, everyone takes note of Gohan's power and he goes to Kami's for training. This helps make the Earthlings stronger through sparring with him once he's ready, though not by enough to change much. Without Piccolo there to help, Kuririn and Gohan are most likely killed by Nappa before Goku can get there and Vegeta later kills Goku. Vegeta then goes to Namek and, even being sneaky enough to bide his time, most likely can't overcome Zarbon even with a Zenkai and definitely doesn't overcome Reacoom.
Assuming he didn't eradicate all life on Earth, #17 and #18 still show up to terrorise the planet without resistance, killing Freeza if he ever chooses to show up. Cell likely absorbs them when he leaves the lab a few decades later and goes into space upon doing so, possibly fighting Dabura at some point and eventually overcoming him. All the factors that would cause Super's arcs to occur are non-existent at this point, so Universe 7 remains Cell's playground essentially until Zen-Oh or the Daishinkan decide to erase it.