Drive mode :
The drive mode you select will change the pedal reaction, the power delivery accel and car behaviour. For a more agressive reaction, the SPORT will be more responsive to pedal input but the downside is the ICE engine will run and your fuel consumption will be less efficient. I do think most PHEV owners run in ECO, since we like hypermiling and we hate burning dinosaur juice. The ECO mode will make the car a bit more "asleep", but this mode is to save fuel and battery.
Remember that Power = (Force x Displacement ) / Time. The faster you want to do something, the more power it needs.
EV mode Accel :
Most EV's are pretty zippy at lower speeds, its just inherent to the torque advantage of an electric drive and the Tucson PHEV often launches in AWD mode, even on dry pavement. But, merging at highway speeds will always request a lot of power and most PHEV do not shine in terms of accel at highway speeds, because the EV motor is small. My previous Ioniq PHEV was horrible and not able to merge on the highway at a safe speed and most of the time and the ICE always had to kick in.
Good news, IMO the Tucson is way better and can merge at safe highway speeds if you have a bit of room to gently accel in the lane. In my case, 9 times out of 10 I can do it in EV mode only. The ICE kick in when I have to merge from 0kmh into a ramp that goes uphill. When you accel, if you are in ECO mode, the right dial gauge will show you where the power request is. As soon you drive the car in the "Power" zone for a little time, the ICE will turn ON to complement the EV motor for the merge (if you are in ECO mode).
Remember that when you are in EV mode, only the electric motor of 90 HP (67 Kw) is driving the wheels unless you request more power. I'm always impressed how a small electric drive of 90Hp is sufficient. After a couple weeks of driving, you will not look at the power gauge anymore and you will get used to the power delivery of your Tucson PHEV. You will know just by the feeling where the top of the electric 90 HP is, just by feeling. Now, after some time, I can tell when I'm getting close to exceed the 90 HP, and I don't even look at the ECO driving gauge anymore.
This is normal. The Tucson suspension is on the firm side for an SUV, most reviewers do highlight this feature in their reviews (I know Alex On Auto did). This is a personal preference, I do prefer a firmer ride when compared to a sluggish Toyota or Mitsubishi suspension, but yes, the Tucson PHEV is on the rough side for a SUV and you can sure feel the poor Canadian roads.
Remember also that this vehicle is heavy, with the added battery pack.
I hope you'll like it a lot