Luca Connell is reported to be highly rated by the Republic of Ireland staff as reported here. He signed for Celtic on a four-year deal after a mere 674 minutes in the English Championship and two appearances in the FA Cup.
Not much data to go on, but here it is! All numbers are per 90m.
Position
Connell has played primarily as a defensive central midfielder or central midfielder. He is left footed.
Peer Group
There are only five players under 20 who appeared in the English Championship and are classified as central midfielders.
One, Reece James, is one of many loaned out by Chelsea and he appeared mainly as a right wing back.
Another Chelsea loanee, Trevor Chalobah, appeared 34 times for relegated Ipswich Town.
Next comes Rekeem Harper, rumoured to be interesting this parish. He appeared 13 times for West Bromwich Albion. It is reported he is very highly rated.
Then you have Connell. With 10 appearances and 674 minutes, he rated 6.57 on WhoScored?
This gives you some insight on how hard it is for a young player to get game time in that league. Only 10 players of all positions under 20 played in at least 10 matches in the English Championship. Of those, Connell rates 5h on overall WhoScored? rating. Just ahead of Rekeem Harper and Jack Clarke now transferred from Leeds Untied to Tottenham Hotspur.
Defensive
Connell is primarily a deep lying midfielder, and therefore it is appropriate to compare his defensive output to Brown.

Usual caveats apply:
Comparing data from different sources = potentially different definitions. I am particularly suspicious that tackle, intercept, dribbled past and blocks will be inconsistently measured.
Different leagues / styles.
Very different playing for Celtic versus SPFL sides than for Bolton Wanderers at the bottom of the English Championship.
That being said, Connell makes fewer tackles than Brown, which may not surprise. He is particularly weak aerially, winning only 31% of duels compared to Brown’s 63%.
Connell really only out scores Brown on Blocked Shots.
His overall contributions are going to be much lower than Brown’s in a dominant side. We are comparing an 18-year-old with one of the most decorated and respected central midfielders of his age. But it indicates the direction of travel he would need to develop towards.
Ball Progressing / Creativity

Connell of Bolton Wanderers has less than half the passing possession than Brown of Celtic. He still manages a respectable 0.3 key passes per 90m.
He is credited with an assist in a FA Cup tie but I do not have the data for that.
Where WhoScored? is helpful is in breaking down the pass type more granularly that I have the time/patience or ability to capture.
Connell completes 3.7 long passes per 90m, which ranks 24th out of 97 English Championship central midfielders with more than 9 appearances. 3.5 are inaccurate.
He takes set plays and completes 0.7 (0.4 corners, 0.3 free kicks) set play passes per 90m whilst 1.8 are inaccurate.
Whilst Brown only completes 0.32 dribbles per 90m, Connell completes 1.2. With 0.7 being unsuccessful, his Dribble Success of 63% is 1% better than McGregor and higher than all other Celtic midfielders and forwards.
Goal Threat
Connell does not yet have a senior goal, whilst this season Brown was prolific by his standards, with 3!

Based on this small sample, Connell is more accurate and takes double the number of shots Brown attempts.
He is also adept at set piece shots with 0.3 per 90m.
The vast majority of shots are from outside the box. This is not a good predictor of success as these will be low xG efforts.
Most interesting is that half Connell’s shots are with his right foot and half with his stronger left. I love a two footed player! 85% of Brown’s shots are with his right foot. Not surprisingly Connell has no attempts with his head given the aerial duel data above.
Strengths and Weaknesses
With thanks again to WhoScored? here are his strengths and weaknesses according to their data.

Summary
It is a very small data sample. But very few players Connell’s age are pitched into the English Championship central midfield. He rates highly amongst that small pool.
The WhoScored? summary is fair – a dribbling, tackling central midfielder who like a long shot and has set play taking skills. His one obvious weakness is aerial ability.
Of course, we cannot compare him to Brown but this serves as a bench mark for him to aspire to.
Fáilte go Celtic, Luca, agus ádh mór!