I don't think small militias like ttp would be a problem for Taliban though they got the potential to disrupt Taliban,but Taliban is very much committed & disciplined force as we have seen since 2 decades how they defeate NATO & US.
The real problem lies in how they will come to terms with present Afghan government which Taliban always denied their legitimacy & called them puppets of western countries.The ideology is totally opposite between them.Taliban is waiting just for US forces to withdraw their forces from Afghanistan,I won't be surprised once US forces leave Taliban will attack Kabul by all the corners & capture remaining provinces.Deal between America & Taliban seems to be same.These intra afghan talks are just for buying the time For US forces to leave the country with some honour or just face saving.There will be no deal between Taliban & so called Afghan government,it will be just for time consuming.Taliban has categorically mentioned they want same Islamic emirates of Afghanistan which they created in 1996 under mullah Mohammad omar.Taliban will never compromise anything less than that,same time why they should not,they are having the upper hand,they immerged as victorious against a super power.History is witness that vicotorious forces always dictate the terms,it is just matter of time when we are going to see Taliban ruling whole Afghanistan.They will just be little lenient towards northern alliance for the brief time,their might be a reconciliation with them but that too might be on terms of Taliban.The Taliban of 2020 is much more committed & disciplined than 2001.Taliban has learned from their past mistakes,this time they won't isolate themselves before world.instead they will reach out to the world with their point of view.The reason for that is Taliban is now an ideology which world recognizes.The potential of Taliban has been admitted by NATO & US.When NATO & US attacked Taliban in October 2001 they thought it will take 1,2 years for them to crush or annhilate taliban existence from Afghanistan but what happened world saw it.Taliban defeated a super power without any artillary,Tanks or any sophistication matching the opponent.Taliban had no open help from any country still they managed to engage the enemy for almost 20 years with minimal resources.Imagine if they been provided modern warfare weaponery what they will achieve only god knows that as I'm not qualified enough to predict that scenario.